2018年3月30日星期五

10GBASE-T – Will It be the Best Media Options for 10G Data Center?

by Fiber-MART.COM
Ratified in 2006, 10GBASE-T is the standard to provide 10Gbqs connections over balanced twisted-pair copper, including Category 6A unshielded and shielded cabling. It provides great flexibility in network design due to its 100-meter reach capability. An immediate use for 10GBASE-T is to build the data center access-layer network that connects servers to access switches. But is it the best options for 10G data center? Understanding this requires an examination of the pros and cons of current 10GbE media options.
 
10GBASE-CX4
10GBASE-CX4 was the first favorite for 10GbE deployments, however its adoption was limited by the bulky and expensive cables, and its reach is limited to 15 meters. The large size of the CX4 connector prohibited higher switch densities required for large scale deployment. Larger diameter cables like 10GBASE-CX4 are purchased in fixed lengths resulting in challenges to manage cable slack. As a result, pathways and spaces may not be sufficient to handle this larger cable.
 
SFP+
SFP+’s support for both fiber optic cables and DAC which makes it a better solution than CX4. SFP+ is commonly used for 10G today, but it has limitations that will prevent itself from moving to every server. The following image shows a SFP+ nodule, SFP+ DAC cable and a 10GBASE-T SFP+ port media converter.
 
10GBASE-SR—10GBASE-SR (SFP+ fiber) fiber is great for its low latency and longer distance (up to 300 meters), but it is expensive. SFP+ fiber offers low power consumption, but the cost of laying fiber networking everywhere in the data center is prohibitive. The SFP+ fiber electronics can be four to five times more expensive than their copper counterparts, meaning that ongoing active maintenance, typically based on original equipment purchase price, is much more expensive. In addition, replacing a copper connection that is readily available in a server to fiber creates the need to purchase not only the fiber switch port, but also a fiber NIC for the server. EX-SFP-10GE-SR is compatible Juniper SFP+ transceiver that requires a OM3 cable to realize its 10G connectivity, which is an indispensable component for a 10G network.
 
10GBASE-SFP+ DAC—DAC is a lower cost alternative to fiber, but it can only reach 7 meters and it is not backward-compatible with existing GbE switches. Take MA-CBL-TA-1M as an example, it is designed to cover a distance of 1m for 10G connectivity. The DAC cables are much more expensive than structured copper channels, and cannot be field terminated. This makes DAC more expensive than 10GBASE-T. The adoption rate of DAC will be low since it does not have the flexibility and reach of 10GBASE-T.
 
10GBASE-T
The major benefit of 10GBASE-T is that it offers the most flexibility, the lowest cost media, and is backward-compatible with existing 1GbE networks. Like all BASE-T implementations, 10GBASE-T covers a lengths up to 100 meters, which gives network designers a far greater level of flexibility in connecting devices in the data center and the most flexibility in server placement since it will work with existing structured cabling systems. For higher grade cabling plants (category 6A and above), 10GBASE-T operates in low power mode on channels under 30 m. This means a further power savings per port over the longer 100m mode. And because 10GBASE-T is backward-compatible with 1000BASE-T, it can be deployed in existing 1GbE switch infrastructures in data centers that are cabled with CAT6 and CAT6A (or above) cabling, enabling network designers to keep costs down while offering an easy migration path to 10GbE.
 
One challenge with 10GBASE-T is that the early physical layer interface chips (PHYs) consumed too much power for widespread adoption. But there comes a good news with 10GBASE-T is that the PHYs benefit greatly from the latest manufacturing processes. The newer process technologies will reduce both the power and cost of the latest 10GBASE-T PHYs. The latest 10GBASE-T adapters require only 10 W per port. Further improvements will reduce power even more. In 2011, power dropped below 6 W per port, making 10GBASE-T suitable for motherboard integration and high-density switches.
 
Conclusion
Of all the media options offered above, 10GBASE-T breaks through important cost and power consumption barriers in 10GbE deployment as well as its backwards compatibility with 1GbE networks. Deployment on 10GBASE-T will simplify data center infrastructures, making it easier to manage server connectivity while delivering the bandwidth needed for heavily virtualized servers and I/O-intensive applications. I must say, 10GBASE-T will be the best option for 10GbE data center cabling in the near future.

10G Connectivity – Comparing XFP With SFP+

by Fiber-MART.COM
Defined in 2002, XFP (10 Gigabit Small Form Factor Pluggable) is a hot-swappable and protocol-independent transceiver for 10G high-speed computer network and telecommunication links. Except for XFP, there are SFP and SFP+ transceivers available for 10G connectivity. These devices plug into a special port on a switch or other network device to convert to a copper or fiber interface. So what is the difference between them? The following passage will provide a satisfying solution to you.
 
What Is XFP?
XFP is 10 Gigabit transceiver operating at wavelengths of 850nm, 1310nm or 1550nm. This module combine transmitter and receiver functions in one compact, flexible, and cost-effective package. The physical dimensions of the XFP transceiver are slightly larger than the original small form-factor pluggable transceiver (SFP). XFP transceiver modules are available with a variety of transmitter and receiver types including the SR, LR, ER and ZR. The maximum working distance of XFP SR is 300 meters. 10GBASE-LR XFP transceivers have a wavelength of 1310nm and a transmission distance up to 10 km. For example, XFP-10G-L-OC192-SR1 covers a distance of 10km with LC connectors. XFP-10GLR-OC192SR is Cisco XFP 10GBASE-LR/-LW operating at wavelength of 1310nm over singlemode fiber with a links length of 10km. Both 10GBASE-ER XFP and 10GBASE-ZR XFP modules have a wavelength of 1550nm, and the maximum transmission distance of 40km and 80km, respectively.
 
What Is SFP/SFP+?
SFP is most often used for Fast Ethernet of Gigabit Ethernet applications and can support speed up to 4.25Gbps. It interfaces a network device motherboard (for a switch, router, media converter or similar device) to a fiber optic or copper networking cable. It is specified by the SFP transceiver multi-source agreement. The standard SFP transceiver, SFP+ supports speeds of 10Gbps or higher over fiber. The SFP+ product family includes cages, connectors, and copper cable assemblies. It is also similar to the performance requirements of SFF-8431 and also supports 8G Fiber Channel and 10G Ethernet applications. Take 46C3447 as an example, it is 10GBASE-SR SFP+ that can support a distance of 300m over OM3 cable.
 
What’s the Difference Between XFP and SFP+?
First of all, both of them are 10G transceiver modules and can contact with other types of 10G modules. The primary difference between SFP+ and the slightly older XFP standard is that the SFP+ moves the chip for clock and data recovery into a line card on the host device. This makes SFP+ smaller than XFP, enabling greater port density. Because of the smaller volume, SFP+ transfer signal modulation function, serial/deserializer, the MAC, clock and data recovery (CDR) and electronic dispersion compensation (EDC) function from the module to the Lord on the card. In addition, SFP+ compared to XFP, is a more compact factor package. The cost of SFP+ is also less than that to the XFP, X2 and XENPAK. It can connect with the same type of XFP, X2 and XENPAK as well. Therefore, SFP+ is more popular than XFP for 10G network.
 
Summary
10G optical transceivers are designed for 10G or 10Gbit/s data transmission applications including 10 Gigabit Ethernet, 10Gbit/s Fibre Channel, Synchronous optical networking. After years of development, there has been various different form factors and optics types introduced including XENPAK, X2, XFP and SFP+. But up to now, SFP+ is the most commonly used 10G transceivers available on the market. Fiberstore provides a large selection of 10G transceivers with minimum price and high quality. If you have any requirement of our products, please contact us directly.

10G Fiber Optic Transceivers

by Fiber-MART.COM
10GbE technology nowadays is becoming more pervasive as enterprises grow their networks and support more bandwidth-intensive application. In the meanwhile, 10GbE functionality can provide immediate performance benefits and safeguard a company’s investment well into the future. The supporting 10G fiber optic transceivers are designed for 10Gbit/s data transmission applications including 10 Gigabit Ethernet, 10 Gbit/s Fiber Channel, Synchronous optical networking. After years of development, there has been various different form factors and optics types introduced—10G XENPAK, 10G X2, 10G XFP and 10G SFP+. This article will have a brief introduction to these 10G optical transceivers.
 
XENPAK
 
XENPAK is the first 10G fiber optic transceiver. It is a highly integrated, serial optical transponder module for high-speed, 10Gbit/s data transmission application. XENPAK modules designed XAUI interface and knowledge shaping (CDR) function, which comply with the XENPAK MSA protocol and satisfy the application of 802.3ae Ethernet protocol 10GB. The working distance of Xenpak can reach up to 10km over G652 single-mode fiber. Newer Xenpak while using 10GBASE-LX4 standard operated using wavelengths on legacy multimode fibers at distance of up to 300 meters, eliminating the necessity to reinstall cable in a building when upgrading certain 1 Gbit/s circuits to 10 Gbit/s.
 
X2
 
10G X2 has the same function with Xenpak modules and provides robust thermal performance and electromagnetic shielding, but it is only half the size of Xenpak transceiver. X2 is initially centered on optical links to 10 kilometers and is ideally suited for Ethernet, Fibre Channel and telecommunication switches and standard PCI (peripheral component interconnect) based server and storage connections. The 10GB X2 fiber optic transceivers series include X2-10GB-SR, X2-10GB-LR, X2-10GB-ER and X2-10GB-ZR, they are designed based on the X2 MSA and IEEE802.3ae. They’re created for the integrated systems solution, fiber optics distributor along with other IT distributors.
 
XFP
 
Developed after 10G X2 module, XFP is really a standard for high-speed computer network and telecommunication links which uses optical fiber. They sometimes operate at near-infrared wavelengths (colors) of 850 nm, 1310 nm or 1550 nm. Principal applications include 10 Gigabit Ethernet, 10 Gbit/s Fibre Channel, synchronous optical networking (SONET) at OC-192 rates, synchronous optical networking STM-64, 10 Gbit/s Optical Transport Network (OTN) OTU-2, and parallel optics links. They can operate over a single wavelength or use dense wavelength-division multiplexing techniques. XFP modules make use of an LC fiber connector type to achieve high density. The 10G XFP fiber optic transceivers series include XFP-10G-MM-SR, XFP-10GLR-OC192SR, XFP-10G-L-OC192-SR1 and XFP-10GZR-OC192LR. XFP-10GLR-OC192SR is Cisco 10GBASE-LR/LW XFP operating at wavelength of 1310nm for a distance of 10km.
 
SFP+
 
10G SFP+ transceivers are multi-purpose optical modules for 10Gbit/s data transmission applications at 850 nm, 1310 nm and 1550 nm. The transceiver complies with Gigabit Ethernet as specified in IEEE 802.3 and Fiber Channel FC-PH, PH2, PH3 and FC-PI 10.0. Additionally, it provides a unique enhanced digital diagnostic monitoring interface, which allows real-time access to device operating parameters such as transceiver temperature, laser bias current, transmitted optical power, received optical power, and transceiver supply voltage.
 
This SFP+ hot-pluggable transceiver features duplex LC connector and provides up to 1.25 Gbps bi-directional data transfer rate. It supports transmission distances of up to 300 m (984.25 ft) for 62.5/125μm MMF and 500 m (1640.42 ft) for 50/125μm MMF fiber cabling. The 10G SFP fiber optic transceivers series include SFP-10G-SR, SFP-10G-LRM, SFP-10G-LR, SFP-10G-ER, SFP-10G-ZR, SFP-10G-LW, SFP-10G-LH, SFP-10G-LX and SFP-10G-ZW. Cisco 10 gig SFP like SFP-10GB-SR is 10GBASE-SR SFP+ with DOM support. It provides 10GBase-SR connectivity for up to 300 meters with multimode fiber. This 10 Gigabit Ethernet SFP+ transceivers module provides excellent performance port-dense networks with challenging thermal environments, which are ideally suited for datacom and storage space network (SAN/NAS) applications based on the IEEE 802.3ae and Fibre Channel standards, Fibre Channel, 1000Base-SX Ethernet.
 
To sum up, XENPAK is the very first MSA transceiver module for 10GE coupled with the biggest form factor. X2 was later competing standards with smaller form factors. XFP came after X2. SFP+ offers a smaller form factor and also the ability to offer 1G/10G combo ports on hardware. Fiberstore supplies high-quality 10G fiber optical transceivers. All the mentioned 10G optical transceivers (Xenpak, X2, XFP and SFP+) are offered at Fiberstore. Besides 10G optical transceivers, 10G SFP+ DAC cables are also available. If you have any requirement of our products, please send your request to us.

2018年3月29日星期四

What Is Fiber Optical Connectors

by Fiber-MART.COM
Fiber optic connectors, detachable (active) device connected between the fiber and the fiber, the two fiber end face precision docking up to launch the optical output of light energy to maximize the coupling to the receiving fiber,and because of its involvement in the optical link system impact be minimized, which is the basic requirements for fiber optic connectors. To a certain extent, fiber optic connectors affect the reliability and the performance of optical transmission systems.
 
Fiber Optic Connector is an important components used in the fiber optic network. It is also the key part used in fiber optic patch cord and fiber optic pigtail. There are many kinds of fiber optic connectors.we supply one piece fiber optic connectors various types, including standard connectors and irregular types, epoxy types. And fiber optic types include: SC fiber optic connector, FC fiber optic connector, ST fiber optic connector,LC fiber optic connector,MU fiber optic connector, SC/APC fiber optic connector, FC/APC fiber optic connector, etc. both Single mode fiber optic connector and multimode fiber optic connector available.
 
There are Single mode fiber optic connector and Multimode fiber optic connector, Single mode fiber optic connectors can be with PC, or UPC or APC polish, while Multimode fiber optic connectors only with PC or UPC polish. PC or UPC or APC refer to how we polish the ferrule of the fiber optic connectors. Judging from the out looking, Multimode connectors are usually with black boot or beige color, Single mode PC and UPC ones are usually with blue or black color, Single mode APC is with green color. Insertion loss is important technical data of the fiber optic connectors. The smaller the better. APC insertion loss is smaller than UPC, UPC is smaller than PC.
 
Fiber optical connectors are used to join optical fibers where a connect/disconnect capability is required. There are many types of connectors, the commonly types are LC, SC, FC, ST, MU, E2000.
 
LC is Lucent Connect or Little Connector or Local Connector. Its ferrule diameter is 1.25mm based on standard of IEC 61754-20. They are often found on small form-factor pluggable transceivers.
 
SC is Subscriber Connector or square connector or standard connector. Its ferrule diameter is 2.5mm and based on the standard of IEC 61754-4. SC connectors offer excellent packing density and their push-pull design reduces the chance of fiber end face contact damage during connection; frequently found on the previous generation of corporate networking gear, using GBICs.
 
FC long form is ferrule connector or fiber channel. FC connector has same ferrule diameter as SC but standard (IEC-61754-13). FC connectors need to be mated more carefully than the push-pull types due to the need to align the key, and due to the risk of scratching the fiber end face while inserting the ferrule into the jack. FC connectors have been replaced in many applications by SC and LC connectors.
 
ST long form is straight tip. The ferrule diameter is 2.5mm and according to standard IEC 61754-2. ST has a key which prevents rotation of the ceramic ferrule, and a bayonet lock similar to a BNC shell.
 
MU (Miniature unit Coupling) connector is the SC connector is currently the most used based on the developed world’s smallest single-core optical fiber connector, developed by NTT.
 
More source of fiber optic connectors, please visit at http://www.fiber-mart.com

A Quick Guide To Fiber Optic Power Meter

by Fiber-MART.COM
When you install and terminate fiber optic cables, you always have to test them. A test should be conducted for each fiber optic cable plant for three main areas: continuity, loss, and power. And optical power meters are part of the toolbox essentials to do this. There are general-purpose power meters, semi-automated ones, as well as fiber optic power meters optimized for certain types of networks, such as FTTx or LAN/WAN architectures. It’s all a matter of choosing the right gear for the need.
 
Here is a quick guide to fiber optic power meters and how they work.
 
Optical power meters are commonly used to measure absolute light power in dBm. For dBm measurement of light transmission power, proper calibration is essential. A fiber optic power meter is also used with an optical light source for measuring loss or relative power level in dB. To calculate the power loss, optic power meter is first connected directly to an optical transmission device through a fiber optic pigtail, and the signal power is measured. Then the measurements are taken at the remote end of the fiber cable.
 
Fiber optic power meter detects the average power of a continuous beam of light in an optical fiber network, tests the signal power of laser or light emitting diode (LED) sources. Light dispersion can occur at many points in a network due to faults or misalignments; the power meter analyzes the high-powered beams of long-distance single-mode fibers and the low-power multibeams of short-distance multimode fibers.
 
Important specifications for fiber optic power meters include wavelength range, optical power range, power resolution, and power accuracy. Some devices are rack-mounted or hand held. Others are designed for use atop a bench or desktop. Power meters that interface to computers are also available.
 
The fiber optic power meter is a special light meter that measures how much light is coming out of the end of the fiber optic cable. The power meter needs to be able to measure the light at the proper wavelength and over the appropriate power range. Most power meters used in datacom networks are designed to work at 850nm and 1300nn. Power levels are modest, in the range of –15 to –35dBm for multimode links, 0 to –40dBm for single mode links. Power meters generally can be adapted to a variety of connector styles such as SC, ST, FC, SMA, LC, MU, etc.
 
Generally, multimode fiber is tested with LEDs at both 850nm and 1300nm and single mode fiber is tested with lasers at 1310nm and 1550nm. The test source will typically be a LED for multimode fiber unless the fiber is being used for Gigabit Ethernet or other high-speed networks that use laser sources. LEDs can be used to test single mode fibers less than 5000 meters long, while a laser should be used for long single mode fibers.
 
Most fiber optic power meters are calibrated in linear units such as milliwatts or microwatts. They may also provide measurements in decibels referenced to one milliwatt or microwatt of optical power. Typically, fiber optic power meters include a removable adaptor for connections to other devices. By measuring average time instead of peak power, power meters remain sensitive to the duty cycle of digital pulse input streams.
 
Use fiber optic power meter and other useful fiber optic test equipment to ensure that your fiber optic system will operate smoothly.

Detail Of Single Mode And Multi Mode Fiber Optic Cable

by Fiber-MART.COM
Fiber optic cable has become apparent that fiber-optics are steadily replacing copper wire as an appropriate means of communication signal transmission. They span the long distances between local phone systems as well as providing the backbone for many network systems. Other system users include cable television services, university campuses, office buildings, industrial plants, and electric utility companies.
 
There are three types of fiber optic cable commonly used:  single mode, multimode and plastic optical fiber (POF).  Although fibers can be made out of transparent plastic, glass, or a combination of the two, the fibers used in long-distance telecommunications applications are always glass, because of the lower optical attenuation.  Both multi-mode and single-mode fibers are used in communications, if you need to transmit less data over longer distances, use single mode fiber optic cables. For a greater data capacity over shorter distances, go with multi mode fiber optic cables, with multi-mode fiber used mostly for short distances (up to 500 m),Multi mode is often used for LANs and other small networks. And single-mode fiber used for longer distance links.
 
Single Mode Fiber: Single Path through the fiber
 
Single Mode cable is a single stand (most applications use 2 fibers) of glass fiber with a diameter of 8.3 to 10 microns that has one mode of transmission.  Single Mode Fiber with a relatively narrow diameter, through which only one mode will propagate typically 1310 or 1550nm. Carries higher bandwidth than multimode fiber, but requires a light source with a narrow spectral width.  Single Mode is also referred to as single-mode fiber, single-mode optical waveguide, mono-mode optical fiber and uni-mode fiber. Single-mode fiber gives you a higher rate of transmission, it also can carry the signal up to 50 times farther distance than multimode, at a slightly higher cost.Single-mode fiber has a much smaller core than multimode.
 
Single Mode fiber is used to connect long distance switches, central offices and SLCs (subscriber loop carriers, small switches in pedestals in subdivisions or office parks or in the basement of a larger building). Practically every telco’s network is now fiber optics except the connection to the home.
 
Multi Mode Fiber: Multiple Paths through the fiber
 
Multi-Mode cable has a little bit bigger diameter, with a common diameters in the 50-to-100 micron range for the light carry component (in the US the most common size is 62.5um).Typical multimode fiber core diameters are 50, 62.5, and 100 micrometers.  Multi Mode fiber is used for shorter distances. Most applications in which Multi-mode fiber is used, 2 fibers are used. Multimode fiber gives you high bandwidth at high speeds (10 to 100MBS – Gigabit to 275m to 2km) over medium distances. Light waves are dispersed into numerous paths, or modes, as they travel through the cable’s core typically 850 or 1300nm. Long cable runs (Above 3000 feet 914.4 meters in length), the multiple paths of light are believed to cause signal distortion at the receiving end, resulting in lost packets and incomplete data transmission. IPS recommends the use of single mode fiber in all applications using Gigabit and higher bandwidth.

2018年3月27日星期二

HOW DOES AN OTDR WORK?

by Fiber-MART.COM
Unlike sources and power meters, which measure the loss of the fibre optic cable plant directly, the OTDR works indirectly. The source and meter duplicate the transmitter and receiver of the fibre optic transmission link, so the measurement correlates well with actual system loss. The OTDR, however, uses unique phenomena of fibre to imply loss.
The biggest factor in optical fibre loss is scattering. It is like billiard balls bouncing off each other, but occurs on an atomic level between photons (particles of light) and atoms or molecules. If you have ever noticed the beam of a flashlight shining through foggy or smokey air, you have seen scattering. Scattering is very sensitive to the colour of the light, so as the wavelength of the light gets longer, toward the red end of the spectrum, the scattering gets less. Very much less in fact, by a factor of the wavelength to the fourth power - that's squared-squared. Double the wavelength and you cut the scattering by sixteen times!
You can see this wavelength sensitivity by going outside on a sunny day and looking up. The sky is blue because the sunlight filtering through the atmosphere scatters like light in a fibre. Since the blue light scatters more, the sky takes on a hazy blue cast.
n the fibre, light is scattered in all directions, including back toward the source as shown in Figure 1. The OTDR uses this "backscattered light" to make its measurements. It sends out a very high power pulse and measures the light coming back. At any point in time, the light the OTDR sees is the light scattered from the pulse passing through a region of the fibre. Think of the OTDR pulse as being a "virtual source" that is testing all the fibre between itself and the OTDR as it moves down the fibre. Since it is possible to calibrate the speed of the pulse as it passes down the fibre, the OTDR can correlate what it sees in backscattered light with an actual location in the fibre. Thus it can create a display of the amount of backscattered light at any point in the fibre.

Figure 2 OTDR Display
There are some calculations involved. Remember the light has to go out and come back, so you have to factor that into the time calculations, cutting the time in half and the loss calculations, since the light sees loss both ways. The power loss is a logarithmic function, so the power is measured in dB.
The amount of light scattered back to the OTDR is proportional to the backscatter of the fibre, peak power of the OTDR test pulse and the length of the pulse sent out. If you need more backscattered light to get good measurements, you can increase the pulse peak power or pulse width as shown below.
 
Figure 3 Increasing the pulse width increases the backscatter level
Note on the display shown in Figure 2, some events like connectors show a big pulse above the backscatter trace. That is a reflection from a connector, splice or the end of the fibre. They can be used to mark distances or even calculate the "back reflection" of connectors or splices, another parameter we want to test in singlemode systems.

What Is OTDR Testing?

by Fiber-MART.COM
In many of my previous articles on fiber optic testing, I have mentioned optical time-domain reflectometers (OTDRs). OTDRs are valuable fiber optic testers when used properly. Improper use, however, can be misleading and, in my experience, can contribute to expensive mistakes for the contractor. I have been personally involved in several instances where misapplication of OTDR testing has cost the contractor as much as $100,000 in wasted time and materials. Needless to say, it’s extremely important to understand how to use these instruments correctly.
 
An insertion-loss test made with a light source and power meter is simple and similar in principle to how a fiber optic link works. A light is placed on one end of the cable, and a power meter measures loss at the other end, just like a link transmitter and receiver use the fiber for communications.
 
An OTDR, however, works like radar. It sends a pulse down the fiber and looks for a return signal, creating a display called a “trace” or “signature” from the measurement of the fiber. Two factors contribute to the return signal from the OTDR test pulse: reflectance and backscatter.
 
Reflectance signals are the peaks in the OTDR trace that are produced by the polished fiber end at a connector or cleave where light is reflected back up the fiber.
 
Backscatter is a much smaller signal caused by the interaction of the light with the molecules in the fiber. When light strikes the molecules of the glass, some light is scattered like billiard balls, and a small amount (about 1 millionth) goes back up the fiber to the OTDR where it is amplified and measured. Both reflectance and backscatter are measured in decibels (dB) on the vertical axis of the OTDR trace.
 
Since the OTDR uses a pulse travelling down the fiber as its test signal, the signal varies over time depending on where the pulse is along the length of the fiber being tested. Knowing the speed of light in the glass fiber allows the OTDR to calculate the distance down the fiber at any point on the trace, making the trace a graph of optical power in decibels versus the length of the fiber.
 
When the OTDR signal travels down a length of fiber, the signal is attenuated by the loss in the fiber itself, which is caused by scattering and absorption. This is seen in a trace by a line sloping down, allowing for the measurement of the attenuation coefficient of the fiber. When the test signal pulse goes past a splice, the loss of the splice causes the signal to decrease, which is seen as a drop in the trace line on the OTDR at the distance where the splice is located. If the pulse goes through a connection (a joint made by two connectors), it will show a drop caused by the connection loss and a peak caused by reflectance in the connection. Even areas of high stress on the fiber, such as kinks in the cable, can be detected with the OTDR.
 
If the OTDR provides all this useful information, what could be the drawbacks of using them? For many contractors, cost is the first problem. OTDRs cost about 10 times the price of a light source and power meter, so you need to have a real need for one before making such a large investment. Otherwise, when you need them, you can rent them and charge the expense to the job where they are used.
 
OTDRs are also complex devices. The installer using one needs to know when OTDR testing is appropriate, how to set the instrument up properly and how to interpret traces. Some manufacturers have told contractors that they can use OTDRs anywhere, and all they need to know is “hit the autotest button.” Believing that is what cost several contractors I know so much time and money.
 
Finally, OTDR traces can have many errors that only the trained and experienced user will understand. Any contractor or installer using OTDRs needs to have proper training to recognize ghosts, gainers and other quirks of OTDR traces.
 
Over the next few months, we’ll explore where OTDR use is appropriate, how to use setup parameters to get the best results and how to properly interpret fiber traces. We’ll also look into how these complex devices can fool you and get you into big trouble!

Using an OTDR: How to keep it simple

by Fiber-MART.COM
Communications networks never go slower, never get simpler, and never stay the same. Likewise, certification testing for fiber-optic cabling has also changed.
 
New test equipment and enhanced testing regiments help ensure that cabling can support the new demands placed on networks. Born from legacy test equipment for telecommunications networks, some of these fiber testers were difficult to use. But a new generation of fiber test equipment is designed to make it easy to certify fiber to the latest standards.
 
Not long ago, the state-of-the-art for fiber-optic cabling was the 100Base-FX standard from the Institute of Electrical and Electronics Engineers , which supported a bit rate of 100 Mbits/sec over a channel with an attenuation of 11 decibels (dB). Today, for IEEE 10GBase-S to support a transmission rate 100x higher than 100Base-FX, the transmission channel must attenuate the light by no more than 2.6 dB. It is this tightening of requirements for the physical media that represents a challenge for all components used to build and test a transmission path.
 
A standards-compliant connector can contribute up to 0.75 dB (0.5 dB typical) to the total loss. This would mean that if you patch two fiber segments together, there would be a total of four connectors, which could-even though each individual segment is compliant-result in worst-case loss of 3 dB (4 x 0.75). This exceeds the loss budget left for the entire link, and with a negative allowance left for the fiber itself.
 
More than a loss measurement
It is here where new test methods are required. Installers who work with optical fiber are, no doubt, familiar with the optical loss test set (OLTS). Performing a loss-length test with an OLTS is an essential part of fiber installation. Every link needs to be tested to ensure it is within the loss limits. But an OLTS will only show if a link has passed or failed. If it fails, the OLTS will not show you why it failed, or where.
 
For these answers, an optical time-domain reflectometer (OTDR) comes into play. Using an OTDR need not be complicated or confusing. Understanding a few basic concepts will make OTDR use as straightforward as using a copper certification tool.
 
Testing fiber links as defined by national and international standards, such as the TIA/EIA-568-A and ISO-11801 specifications, includes the use of an OLTS. Recently updated standards that focus on test methods for installed fiber links, such as ISO-14763-3 and TIA TSB-140, now recommend the complementary use of an OTDR. These new standards add the use of an OTDR to verify not just that the link has passed, but to ensure the quality of each installed component on the link.
 
Two levels of testing are defined in these updated standards: Basic (or Tier 1) testing uses an OLTS. Extended (or Tier 2) testing involves the use of an OTDR and an OLTS.
 
The following example helps demonstrate how an extended test regime can help to ensure consistent quality during installation. Assume that the first connector in a 2-connector, 100-meter fiber link performs extremely well, while the second connector is poorly installed or contaminated. In such a circumstance, the measurement with an OLTS may show that the link passed by a slim margin of 0.02 dB, but does not identify the second connector as a bottleneck (noted in bold).
 
Identifying bottlenecks is the strength of an OTDR, which sends a pulse of light into fiber and measures the light reflected back at each component as the light lost at that component. The same is true for backscattered light along the length of the fiber itself.
 
Little setup required
An OTDR can produce accurate, highly detailed measurements, if the correct setup and necessary accessories are employed. Recent versions of standards like ISO-14763-3 make an attempt to specify all necessary elements for a correct measurement with an OTDR, eliminating common sources of measurement error, including:
 
Specifications for launch and receive fibers;
Correct use of launch and receive fibers;
Instructions detailing how to position the cursor for the correct reading of link, component, and segment attenuation;
List of conditions under which it is vital to measure each fiber in both directions.
You may view these setup requirements as overly complex, which may explain why many consider the OTDR to be a tool for experts only. This is also why installers and contractors may choose not to bid on projects that require an OTDR, or subcontract this work to a company specializing in fiber. Such thinkingis in contrast to the certification of twisted-pair copper cabling systems, where after setting the correct standard, a single press of the autotest button does everything.
 
Fortunately, the actual use of the OTDR is not as challenging as it appears. Making sure that test leads, launch fibers, andreceive fibers are in a crisp condition, and are clean and correctly connected, will always be your responsibility. But the remainder of the setup steps can be taken care of by the instrument. Newer OTDRs will create an image of the proper setup configuration. You merely need to make connections and have the instrument “learn” the launch and receive fibers.
 
After this step, the tester will be ready to certify links and all included components for their compliance. Often, a project-specific standard, which is derived from the manufacturer’s data sheet or reference implementation, will be used to set these limits.
 
Pass, fail, or squeak by
When the tester is properly configured, the tests are as simple as copper certification. The most common situation should be that the link passes, and a “pass” indication on the summary screen will indicate the tester evaluated all elements of the link. Results are stored for later reporting. The instrument also automatically subtracts the contribution of the launch and receive fibers from the total link, showing only the total overall loss.
 
While this example is sufficient information for a passing link, you will need to dig deeper and get more-detailed information if the link (or parts of it) failed the specified limits.
 
You can see, for example, that the loss may be 1.07 dB and within the limits, but a single bottleneck contributes 0.92 dB to the overall loss.

2018年3月26日星期一

Why Needs Cisco GLC-LH-SM Transceiver

by Fiber-MART.COM
Fiber optic technology has proven itself as an indispensable component for network backbone and other high-demand applications as it generally offers greater bandwidth than traditional copper cable. However, fiber optic cables are made of a specialized glass-like material that costs more to manufacture than traditional copper networking cables. Additionally, the interfaces on either end of the cable have often been required to be highly complex transceivers that required a large amount of intricate configuration to perform optimally. That’s the main obstacle that has remained to widespread adoption of fiber optic networking.
 
But recently, as technology has improved, the price of fiber optic media has fallen to the degree, thus with its obvious advantages over copper cable, fiber optic cable are feasible and affordable for networking applications. As for the optical interfaces, with Cisco GLC-LH-SM fiber optic transceivers, those obstacles are a thing of the past. Here explains why the GLC-LH-SM transceiver makes fiber optic networking possible.
 
Brief Overview of Cisco GLC-LH-SM
 
Cisco GLC-LH-SM is a 1000BASE-LX/LH SFP for both multimode and single-mode fibers. The 1000BASE-LX/LH SFP, compatible with the IEEE 802.3z 1000BASE-LX standard, operates on standard single-mode fiber-optic link spans of up to 10 km and up to 550 m on any multimode fibers. So now let’s move on the next part. Figure 1 shows a Cisco GLC-LH-SM transceiver module.
 
Every Network needs Cisco GLC-LH-SM
 
One thing that makes optical transceivers so special is that they are hot swappable—a huge development in fiber optic technology. In the past, if designers had to repair a transceiver failure, he would redesign the whole system, which meant a lengthy amount of network downtime. But with Cisco GLC-LH-SM, the whole process will be quite easy. You can leave the power on, remove the device, pop in the replacement, then you network is back off to races as shown in Figure 2.
 
It is necessary to make sure the configuration of an optical transceiver before operating. But this GLC-LH-SM transceiver is preferred by most designers because it doesn’t need to be configured to begin functioning. It is ideal for network designers as it reduces the number of steps required to achieve the desired goal. Sometimes, external calibration is required, but this is not always the case. The most stringent applications will require it, and most other applications will not. This significantly reduces the number of steps or requirements necessary for designing an optimal network.
 
Cisco GLC-LH-SM is compatible with 1000BASE-LX/LH, which makes it possible for both single-mode and multimode fiber. When you need a network solution that covers a long distance, this transceiver operating over single-mode fiber is available for a link span of up to 10km. It is ideal to be deployed in Hospitals, university campuses, and large research facilities. And multimode opens the data floodgates, giving you maximum throughput upwards of 1.25 Gbps.
 
Conclusion
 
There lists three reasons why every network needs GLC-LH-SM transceiver. GLC-LH-SM fiber optic transceiver makes it so much easier to redesign fiber optic technology into your network. It does this, simply, by making it just as easy as to incorporate a traditional Ethernet router. And it doesn’t need to be configured. But besides those reasons, there are countless other reasons, which will help designers recognize why they should select the devices and design them into their networking solutions.
 
If you are in the market for GLC-LH-SM optics, ask an expert for help. He will help you select the proper technology and design what you need to achieve your goals. Every network needs GLC-LH-SM optics, you just have to find the best manufacturer and type to meet your needs. In fact, Cisco original fiber optics are too costly, the similar Cisco GLC-LX-SM-RGD are also very expensive. Thus find a reliable vendor will solve all your problems. As you know Fiberstore would love to answer any questions about GLC transceivers or any other networking questions you may have. Please contact us if you may have any questions.

1.25G SFP Transceiver Solution

by Fiber-MART.COM
SFP optical module is a compact optical transceiver module used in communication field. SFP optical transceivers are designed to support SONET/SDH, Fast Ethernet, Gigabit Ethernet, Fibre Channel and other communications standards. It interfaces a network device motherboard (switch, router, media converter or similar device) to a Fiber Channel or Gigabit Ethernet optical fiber cable at the other end. SFP transceivers are available in a wide range of data rates including 155M, 622M, 1.25G and 2.5G, which allows users to choose the most suitable transceiver for each link. Today’s article will illustrate the most popular 1.25G SFP transceivers.
 
Description of SFP Transceiver
 
SFP modules can be divided into different types according to different standard. Here is what you need to know about SFP modules. The transmission distance of a SFP is up to 120km for single-mode and 2km for multimode fiber. The SFP fiber transceiver could be dual fibers with LC connectors, or single fiber with LC or SC connectors. The wavelengths could be 850nm, 1310nm and 1550nm. The 1.25G SFP optical transceiver modules are available in different standard such as 1000BASE-T, 1000BASE-SX, 1000BASE-LX/LH, etc. The following part explains such types.
 
1000BASE-SX SFP Transceiver
 
1000BASE-SX SFP transceiver is a cost effective 850nm module supporting dual data-rate of 1.25Gbps/1.0625Gbps. It is compatible with the IEEE 802.3z 1000BASE-SX standard and operates multimode fibers link up to 550 m. The fiber optic transceiver consists of three sections: a VCSEL laser transmitter, a PIN photodiode integrated with a trans-impedance preamplifier (TIA) and MCU control unit. This SFP type (e.g. J4858B) is usually applied for Fiber Channel links, Gigabit Ethernet links, Fast Ethernet links, etc. J4858B (see in Figure 1) is HP 1000BASE-SX SFP that is widely welcomed by overall users.
 
1000BASE-LX/LH SFP Transceiver
 
1000BASE-LX/LH SFP transceiver is a high performance 1310nm transceiver for single-mode fibers. It is compatible with the IEEE 802.3z 1000BASE-LX standard and also supports dual data-rate of 1.25 Gbps/1.0625 Gbps with a transmission distance of 10 /15 /20 km. Cisco GLC-LX-SM-RGD (shown in Figure 2) is 1000BASE-LX/LH SFP that can operate on standard single-mode fiber-optic link spans of up to 10 km and up to 550 m on any multimode fibers. HP J4860C is a 1000BASE-LH SFP that can operates over 1550nm for a distance of 70km. Unlike Cisco GLC-LX-SM-RGD SFP, J4860C can support a much longer distance of 70km, which is ideal for long-haul network application.
 
10/100/1000BASE-T SFP Transceiver
 
10/100/1000BASE-T SFP Transceiver is compatible with the Gigabit Ethernet standard as specified in IEEE STD 802.3. It supports data rates of 10/100/1000 Mbps, fully satisfying 10/100/10001000BASE-T applications such as LAN 10/100/1000Base-T Fiber Channel links, Gigabit Ethernet over Cat 5 Cable, Switch to Switch Interface, Router/Server interface, etc.
 
Why Choose Compatible SFP Module
 
We have introduced several SFP modules above including the HP SFPs. The original SFP optical transceivers are very expensive, the simple solution to this is to find a reliable OEM vendor. Besides saving cost, there are many others reasons that you should choose to purchase a compatible SFP, SFP+ or XFP fiber optic transceiver. For example in a scenario where gigabit speed is required to run across a point-to-point link, the distance between the link length is assessed and an appropriate SFP transceiver module native to the host device is chosen. If a HP platform was in situation, then the selection of module will be limited by among the following: 550 meter (J4858B), 10km (J4859B), 40km (JD061A) or the maximum 70km (J4860C). Using a compatible SFP you can choose from a variety of distance limits from 550meters up to 100km in numerous increments with distances of 160km being achievable on the top product lines.
 
Another advantage of use compatible SFP transceivers is the freedom to tailor the transceiver to your individual requirement. Custom serial numbers can be added both to the product label and also hard coded to the device itself. Latches can be color coded for high density link identification Fiberstore also provide a recoding service in China, this specific service means existing SFP's can be adapted if the host device is to be changed. In some instances, even cross-device compatibility is quite possible.
 
Conclusion
 
Because of its high performance and small size, SFP transceiver replaces the former GBIC module and becomes the most used fiber optic transceiver module in the telecommunication industry. Currently, many optical vendors supply optical transceiver modules. Fiberstore, as a professional telecom manufacturer and supplier, offers a full range of SFP optical transceivers that are 100% compatible with large brands. We are committed to provide high-quality products and long-term customer services to our customers. Any interested in our products, you can contact us directly.

How to Choose Between Coaxial Cable, Twisted Pair and Fiber Optic Cables?

by Fiber-MART.COM
As enterprises are striving for high reliability and performance as well as seamless data access and reporting, industrial networks are becoming more sophisticated. In terms of cabling solutions, it is essential to use the industrial Ethernet cable to achieve reliable performance. However, with so many fiber optics for sale, to select a right cable for broadband connection services is challenging. Coaxial cables and twisted pair or fiber optic cables are available for network connectivity. So which one is an ideal choice, coaxial cable or twisted pair cable? Is the fiber optic cable that fits your needs most? This article outlines the coaxial cable, twisted cable and fiber optic cables to help you select the right cable for your network.
 
Describing Coaxial Cable
 
Coaxial cable, or coax cable, is a single wire usually copper wrapped in a foam insulation. Because of its insulating property, coaxial cable can carry analogy signals with a wide range of frequencies. Thus it is widely used in feedlines connecting radio transmitters and receivers with their antennas, computer network connections, digital audio (S/PDIF), and distributing cable television signals. Over time, the industry settled on two characteristic coaxial cable impedances for the vast majority of applications: 50 Ohm and 75 Ohm.
 
The above figure shows the internal structure of the coaxial cables. In the middle of the coaxial cable is what is known as the center conductor. It can be made of either solid or stranded wire and is typically a mix of Aluminum and Copper. Surrounding the center conductor is something called the dielectric. The dielectric acts as a buffer of sorts to keep the center conductor isolated and straight. It usually is comprised of some blend of plastic and/or foam. Finally, on the outside of the dielectric is the coaxial cable’s shield, which is usually a combination of Copper and Aluminum foil and/or wire braid. The shield is then coated by something like PVC to insulate it from the environment.
 
Twisted Pair Cable Overview
 
Twisted pair cable is a type of copper wiring in which two conductors of a single circuit are twisted together. The twisting feature can avoid noise from outside sources and crosstalk on multi-pair cables, so this cable is best suited for carrying signals. Generally it comes in two versions: Shielded Twisted Pair (STP) and Unshielded Twisted Pair (UTP). STP is commonly used in Token Ring networks and UTP in Ethernet networks. Besides STP and UTP cables, twisted pair cables can be alao found in Categories cable. For instance, Cat 6 twisted pair cables are used for 1000BASE-T and 10GBASE-T networks. The image below displays the STP and UTP cables.
 
Finally Comes to Fiber Optic Cable
 
A fiber optic cable is a cable containing one or more optical fibers. Fiber optic cables often contain several silica cores, and each fiber can accommodate many wavelengths (or channels), allowing fiber to meet ever-increasing data capacity requirements. When terminated with LC/SC/ST/FC/MTRJ/MU/SMA connectors on both ends, fiber optic cables can achieve fiber link connection between equipment during fiber cabling. Nowadays, two types of fiber optic cables are widely adopted in the field of data transfer—single mode fiber optic cables and multimode fiber optic cables. Take LC to ST fiber cable for example, the LC to ST 10G OM4 multimode fiber cable (seen in the below image) is utilized for 10G short-reach applications, while the LC to ST single-mode fiber cable can be used for long-reach application.
 
Comparison Between These Cables
 
When considering which kind of fiber cable is appropriate for network services, one thing you should keep in mind that each type of cable has its unique advantages and disadvantages concerning about these factors—cost, speed, security, reliability, bandwidth, data carrying-capacity, and so on.
 
Coaxial Cable can be installed easily, relatively resistant to interference. However, it is bulky and just ideal for short length because of its high attenuation. It would be expensive over long-distance data transmission. While Twisted Pair Cable is most flexible and cheapest among three kinds of cables, easy to install and operate. But it also encounters attenuation problem and offers relatively low bandwidth. In addition, it is susceptible to interference and noises.
 
As for fiber optic cables, it is treated as the most popular mediums for both new cabling installations and upgrades, including backbone, horizontal, and even desktop applications. Compared with the other two cables, fiber optic cable is small in size and light in weight, and the conductor is glass which means that no electricity can flow through. In addition, fiber cable is immune to electromagnetic interference. The biggest advantage of fiber optic cable is that it can transmit a big amount of data with low loss at high speeds over long distance. Nevertheless, it needs complicated installing skills, difficult to work with and expensive in the short run.
 
Conclusion
 
With all the features and disadvantages of the cables listed above, it is time for for you to make your won choice. Note that the cost of the cable is compared to the high costs of network failure, which can be thousands of dollars per minute. Therefore it is make sense to choose and install the right cable for your LAN network. fiber-mart.COM provides a full range of fiber optics including the cables, optical transceivers, patch panels, and fiber enclosures, etc. Other cables such as Cat 5e, Cat 6, Cat 6A are also available for your copper networks. Welcome to visit fiber-mart.COM for more detailed information.

2018年3月25日星期日

Fiber Optic Cable and Connector Selection

by Fiber-MART.COM
Proper selection of fiber optic cables and connectors for specific uses is becoming more and more important as fiber optic systems become the transmission medium for communications and aircraft applications, and even antenna links. Choices must be made in selecting fiber optic cables and connectors for high-reliability applications. This article provides the knowledge for how to make appropriate selections of fiber optic cable and connector when designing a fiber optic system.
 
Fiber Optic Cable Selection
To select a fiber optic cable, you have to make choices of both the fiber selection and the cable construction selection.
 
Fiber Selection
The three major fiber parameters used in selecting the proper fiber for an application are bandwidth, attenuation and core diameter.
 
Bandwidth: The bandwidth at a specified wavelength represents the highest sinusoidal light modulation frequency that can be transmitted through a length of fiber with an optical signal power loss equal to 50 percent of the zero modulation frequency component. The bandwidth is expressed in megahertz over a kilometer length (MHz/km).
 
Attenuation: The optical attenuation denotes the amount of optical power lost due to absorption and scattering of optical radiation at a specified wavelength in a length of fiber. It is expressed as an attenuation in decibels of optical power per kilometer (dB/km). The attenuation is determined by launching a narrow spectral band of light into the full length of fiber and measuring the transmitted intensity.
 
Core Diameter: The fiber core is the central region of an optical fiber whose refractive index is higher than that of the fiber cladding. Various core diameters are available to permit the most efficient coupling of light from commercially available light sources, such as laser diodes. There are two basic fiber types, single-mode and multimode. Single-mode fiber has a core diameter of 8 to 10 microns and is normally used for long distance requirements and high-bandwidth applications. Multimode fiber has a core diameter of 50 or 62.5 microns and is usually used in buildings. The picture below shows single-mode and multimode fiber with different core diameters.
 
 
Cable Construction Selection
Another important consideration when specifying optical fiber cable is the cable construction. There are three main types of cable configurations: buffered fiber cable, simplex cable and multichannel cable.
 
Buffered Fiber Cable: There are two kinds of buffered fiber. The first is a loose buffer tube construction where the fiber is contained in a water-blocked polymer tube that has an inner diameter considerably larger than the fiber itself. The loose buffer tube construction offers lower cable attenuation from a given fiber, and a high level of isolation from external forces. Loose buffer cables are typically used in outdoor applications and can accommodate the changes in external conditions. The second is a tight buffer tube design. A thick buffer coating is placed directly on the fiber. The tight buffer construction permits smaller, lighter weight designs and generally yields a more flexible cable. A comparison of these two cable constructions is shown below.
 
Simplex Cable: A simplex fiber optic cable has only one tight buffered optical fiber inside the cable jackets. Simplex fiber optic cables are typically categorized as interconnect cables and are used to make interconnections in front of the patch panel. They are designed for production termination where consistency and uniformity are vital for fast and efficient operation.
 
Multichannel Cable: Building multiple fibers into one cable creates a multichannel cable. This type of cable is usually built with either a central or external strength member and fiber bundled around or within the strength member. An external jacket is used to keep the cable together.
 
Fiber Optic Connector Selection
Connector is an integral component of the cabling system infrastructure, which keeps the information flowing from cable to cable or cable to device. There are various connector types, including LC, FC, ST, SC, MTRJ, MPO, MTP, DIN, E2000, MU, etc. To design a fiber optic system, optical connector selection is also a very important decision. When selecting an optical connector, you have to take fiber types, polishing styles and number of fibers all into consideration.
 
Polishing Styles: There are mainly three kinds of polishing styles, PC (physical contact), APC (angled physical contact), and UPC (ultra physical contact). PC, UPC and APC refer to how the ferrule of the fiber optic connectors is polished. PC connector is used in many applications. UPC connectors are often used in digital, CATV, and telephony systems. APC connectors are preferred for CATV and analog systems. The picture below shows these three kinds of polishing styles.
 
Fiber Types: Single-mode and multi-mode optical fiber are two commonly used fiber types. Accordingly, there are single-mode optical connector and multi-mode optical connector. ST and MTRJ are the popular connectors for multi-mode networks. LC connector and SC connector are widely used in single-mode systems. Single-mode fiber optic connectors can be with PC, or UPC or APC polish, while multi-mode fiber optic connectors only with PC or UPC polish.
 
Number of Fibers: Simplex connector means only one fiber is terminated in the connector. Simplex connectors include FC, ST, SC, LC, MU and SMA. Duplex connector means two fibers are terminated in the connector. Duplex connectors include SC, LC, MU and MTRJ. Multiple fiber connector means more than two fibers (for up to 24 fiber) are terminated in the connector. These are usually ribbon fibers with fiber count of 4, 6, 8, 12 and 24. The most popular ribbon fiber connector is MT connector.
 
Conclusion
The key to designing a successful fiber optic system is understanding the performance and applications of different kinds of fibers, cable constructions and optical connectors, and then utilizing the appropriate components. fiber-mart.com provides a wide range of fiber optic cables and connectors. Fiber optic cables can be available in single-mode, multimode, or polarization maintaining, and they can meet the strength and flexibility required for today's fiber interconnect applications.