2019年8月18日星期日

Patch Cord Types and Their Impact on the Network

Data centers and the networks they support have grown to be an integral part of every business. The software applications that keep mission-critical operations up and running in highly redundant, 24/7 environments rely on highly engineered structured cabling systems to connect the cloud to every user. Structured cabling is the foundation that supports data centers.
 
Although structured cabling isn’t as sexy as diesel-driven UPS systems or adiabatic cooling systems, it plays a huge role in supporting the cloud. One important component of structured cabling that is often overlooked: patch cords.
 
Oftentimes, patch cords are purchased haphazardly and installed at the last minute. But the right patch cord type can improve the performance of your network. The proper design, specification, manufacturing, installation and ongoing maintenance of patch cord systems can help ensure that your network experiences as much uptime as possible.
 
A patch cord problem can wreak havoc on an enterprise, from preventing an airline customer from making a necessary reservation change to keeping a hotel guest from getting work done while on business travel.
 
What Drives Data Growth?
 
Explosive data growth due to social media, video streaming, IoT, big data analytics and changes in the data center environment (virtualization, consolidation and high-performance computing) means one thing: Data traffic is not only growing in bandwidth, but also in speed.  
 
Another essential point is network design. Today’s network design, such as a leaf-spine fabric, makes the network flatter, which lowers latency – this makes the Ethernet and corresponding patch cord types incredibly important.
 
The Definition of a Patch Cord
 
A patch cord is a cable with a connector on both ends (the type of connector is a function of use). A fiber patch cord is sometimes referred to as a “jumper.” 
 
Patch cords are part of the local area network (LAN), and are used to connect network switches to servers, storage and monitoring portals (traffic access points). They are considered to be an integral part of the structured cabling system.
 
Copper patch cords are either made with solid or  stranded copper; due to potential signal loss, lengths are typically shorter than connector cables.
 
A fiber patch cord is a fiber optic cable that is capped at both ends with connectors. The caps allow the cord to be rapidly connected to an optical switch or other telecommunications/computer device. The fiber cord is also used to connect the optical transmitter, receiver and terminal box.
 
Selecting Copper Patch Cords
 
There are many copper patch cord types to consider – but here are a few key elements to keep in mind.
 
Size: A copper patch cord with a smaller OD (outside diameter) takes up less space, and also has a smaller bend radius. This allows it to be deployed in space-deprived environments, and offers more working space for potential expansion in the future.
Twinning: A stable and consistent twinning process (the twisting of copper conductors) helps maintain internal cable characteristics and reduce signal loss during physical manipulation.
Bonded-Pair Technology: The process of bonding individual conductors along the longitudinal axis guarantees uniform spacing between the twisted pair, as well as reliable electrical performance.
Types of Testing: Transmission performance depends on the integrity of the system, including cable characteristics, connecting hardware, cross-connect wiring and patch cords. Manufacturer testing and post-installation testing ensure that the network remains reliable and 100% available.
Length: Pay attention to length restrictions for twisted pairs.
Connections: Look for snagless, over-molded engineered boots, which offer strain and pull relief to protect patch cords from damage.
Traceability: Having the ability to trace a patch cord’s connection points improves reliability, reduces troubleshooting time, improves uptime and reduces IT teams’ efforts when making changes.
Selecting Fiber Patch Cords
 
Choosing fiber patch cords requires just as many considerations as choosing copper patch cord types. Before selecting a fiber patch cord, ask yourself:
 
Which connector type is needed? LC, SC, ST, FC, MPO or MTP? Each connector option offers pros and cons. Selecting the right connector can speed up deployment and reduce costs.
Should singlemode or multimode patch cord types be used? Singlemode patch cords are used for long distances; multimode patch cords are used for shorter distances.
Are simplex (one connector per end) or duplex (two connectors per end) cable connections necessary?
How long should the patch cord be? For example, fiber patch cords are available in lengths of 2 m, 3 m or 5 m. The right patch cord length will eliminate slack and potential damage due to kinking.
What type of cable jacket is needed? Depending on the installation location (plenum, underfloor, exterior or floor mounted), the exterior cabling jacket is available in a variety of configurations to protect the cable’s insulation and conductor core. Selecting the right jacket – single jacket, plenum rated, double jacket/armored, double jacket/heavy duty, etc. – for the right environment will ensure proper performance.
The demand for higher bandwidth and faster network speeds requires a network that can handle higher compute densities without sacrificing reliability.
 
Selecting, installing and maintaining the right patch cord type affects today’s network in many ways. Belden’s copper and fiber patch cords offer superior performance and engineered resiliency to meet the bandwidth and network speeds of today, tomorrow and beyond.

SELECTING A FIBER OPTIC PATCH CORD

Your Guide to Selecting the Perfect Patch Cord for the Job
I receive many questions when it comes to the topic of Networks and Datacom, but one subject I believe many can benefit from is how to determine the differences between one fiber optic patch cord and another. Now, fiber optic patch cords come in a variety of cable and connector types. In order to obtain the proper patch cord you need to determine several attributes:
 
Cable Type — Fiber Optic cable comes in two general types, Single-Mode and Multi-Mode fiber.
 
Single-Mode fiber cable generally has a 9 Micron diameter glass fiber. There are two sub groups (referred to as OS1 and OS2) but most cable is "dual rated" to cover both classifications.
 
Multi-Mode fiber cable can have several different diameters and classifications of fiber strands.
The two diameters currently in use are 62.5 Micron and 50 Micron.
Within the 50 Micron diameter Multi-Mode cable, there are three different grades (referred to as OM2, OM3, and OM4). The cable types used in the patch cord should match that of the network cabling to which they are attached via the patch panel.
 
The fiber cable may be available in different "jacket diameters" (such as 2mm or 3mm). Thinner diameters (1.6 or 2mm) may be preferable in dense installation within a single rack since they take up less space and are more flexible.
 
Cables that route from rack to rack (especially via cable tray) may be more suitable if they have the thicker jacket that results in larger diameters thus making them more rigid.
 
Flammability of the jacket material could become an issue if the area they are in has special requirements for flame spread or products of combustion in case of a fire. In these cases, patch cords may have to be classified as "Plenum Rated" (OFNP) rather than "Riser Rated" (OFNR).
Simplex or Duplex — Unlike copper patch cords which send information in both directions (having multiple pairs of conductors with which to do so), most fiber patch cord cables have a single strand of fiber allowing for signal flow in one direction only.
 
Connecting equipment so that it can send and receive information requires two strands of fiber (one to transmit and one to receive information). This can be accommodated by using two "Simplex" (single strand of fiber) cables for each equipment interconnection or a "Duplex" cable, with conductors and/or connectors bonded together in pairs.
 
Length — Overall length of the patch cord may be specified in feet or meters, depending on your preference.
 
Connector Type — See the connector type descriptions below. Some patch cords may have different connector types on each end to accommodate interconnection of devices with dissimilar connectors. In some cases, there may be a connector on only one end, and bare or unterminated fiber on the other. These are usually referred to as "Pigtails" rather than "Patch Cords".
 

How to buy the best quality Singlemode Fibre Optic Patch Leads?

Are all optic fibre patch cords created equal
Many people would answer yes to this question, as from first glance they all look physically similar. However, upon closer inspection and by measuring performance, it is quite obvious that the quality can vary greatly.
 
For many people in the IT and telecoms industry, a fibre optic patch lead (also known as an optic fibre patch cord) is now considered a commodity item.
 
However, when choosing to buy the best quality singlemode fibre optic patch leads, the following should be considered:
 
What is Fibre Optic Patch Lead Connector Grade (Performance)?
IEC standards dictate the connector performance requirement for each grade of fibre optic patch lead connector. These standards guide end users and manufacturers in ensuring compliance with best practices in optical fibre technology.
 
Generally, Grade A, B or C options are available, with Grade A providing the best performance.
 
According to IEC 61753 and IEC 61300-3-34 Attenuation Random Testing Method, ‘Grade C’ connectors have the following performance characteristics: Attenuation: 0.25dB mean, >0.50dB max, for >97% of samples. Return Loss: >35dB.
 
‘Grade B’ connectors have the following performance characteristics: Attenuation: 0.12dB mean, >0.25dB max, for >97% of samples. Return Loss: >45dB.
 
‘Grade A’ connector performance (which is still yet to be officially ratified by IEC) has the following performance characteristics: Attenuation: 0.07dB mean, >0.15dB max, for >97% of samples. While the Return Loss using IEC 61300-3-6 Random Mated Method is >55dB (unmated – only angled connectors) and >60dB (mated), this performance level is generally available for LC, A/SC, SC and E2000 interfaces.
 
What Singlemode Optic Fibre Types are available?
For singlemode fibre optic patch leads, two fibre types are generally available, G652D or G657A2.
 
G652D and G657A2 specifications refer to the glass and cable construction of optical fibre and are generally the fibres of choice in optical fibre patch leads for singlemode systems.
 
657A2 optical fibre in patch leads, provide an improved bend radius and flexibility, which may allow for better cable management and routing in congested areas. The improved bend radius may also allow for increased density in high-density patching fields. G657A2 optical fibre is becoming very popular in Data Centre and Enterprise network deployments.
 
What are Optical Fibre Connector types?
For singlemode optical fibre patch leads, the following connector types are available, LC, SC, SC/A, ST, FC, E2000.
 
The most common types of connectors used in modern transmission systems are SC, SC/A and LC (either simplex or duplex connectors).
 
Selecting the correct patch lead connector type is usually dictated by the transmission equipment or patch panel that the patch lead needs to connect with.
 
Why the Optical Fibre Cable Diameter is important
In high-density patching areas, the selected patch lead cable diameter can either increase or decrease congestion. It is generally recommended that simplex fibre optic patch leads have a diameter of approximately 2mm.
 
When selecting duplex singlemode fibre optic patch leads, there are a couple of options. Firstly, a figure 8 (2 x 2mm cords) patch cord is available, with each connector being physically separated (simplex connector). Secondly, the more common option for duplex fibre patch leads is a round 3mm duplex cable. This option requires the use of a uniboot duplex fibre optic connector, however, the smaller cable diameter helps reduce congestion in patching fields.

2019年8月15日星期四

Somethings you should know about 40GBASE-SR4 QSFP+ Modules

With the growing demand for high data rates, 40 Gigabit Ethernet (GbE) is now becoming more and more widely adopted. For a 40 GbE network application, precise connectivity is crucial. 40G QSFP (quad small form factor pluggable) portfolio offers customers a wide variety of high-density and low-power 40 Gigabit Ethernet connectivity options. Among them, 40GBASE-SR4 QSFP+ transceiver is a common 40 GbE connectivity option. And here are some things that you need to know about 40GBASE-SR4 QSFP+ transceivers.
 
Introduction
40GBASE-SR4 is a fiber optic interface for multimode fiber of OM classes 3 and 4 with four parallel OM3 or OM4 fibers in both directions. “S” means short, indicating that it is an interface for short distances. The “R” denotes the type of interface with 64B/66B encoding and the numeral 4 indicates that the transmission is carried out over a ribbon fiber with four multimode fibers in every direction. Each lane has a 10 Gbit/s data rate. 40GBASE-SR4 QSFP+ modules usually use a parallel multimode fiber (MMF) link to achieve 40G. It offers 4 independent transmit and receive channels, each capable of 10G operation for an aggregate data rate of 40G over 100 meters of OM3 MMF or 150 meters of OM4 MMF. It primarily enables high-bandwidth 40G optical links over 12-fiber parallel fiber terminated with MPO/MTP multifiber female connectors.
 
40GBASE-SR4 QSFP+ module can also be used in a 4x10G mode for interoperability with 10GBASE-SR interfaces up to 100 and 150 meters on OM3 and OM4 fibers, respectively. The worry-free 4x10G mode operation is enabled by the optimization of the transmit and receive optical characteristics to prevent receiver overload or unnecessary triggering of alarm thresholds on the 10GBASE-SR receiver, and at the same time is completely interoperable with all standard 40GBASE-SR4 interfaces. The 4x10G connectivity is achieved using an external 12-fiber parallel to 2-fiber duplex breakout cable, which connects the 40GBASE-SR4 module to four 10GBASE-SR optical interfaces. The picture below shows a Mellanox MC2210411-SR4 compatible 40GBASE-SR4 QSFP+ transceiver.
 
40GBASE-SR4 QSFP+ Module vs 40GBASE-CSR4 QSFP+ Module
40GBASE-CSR4 QSFP+ module is similar to the 40GBASE-SR4 interface extends supported link lengths to 300m and 400m respectively on laser-optimized OM3 and OM4 multimode fiber cables. Each 10-gigabit lane of this module is compliant to IEEE 10GBASE-SR specifications. This module can be used for native 40G optical links over 12-fiber ribbon cables with MPO/MTP connectors, or in 4x10G mode with ribbon to duplex fiber breakout cables for connectivity to four 10GBASE-SR interfaces. Maximum channel insertion loss allowed is respectively 2.6dB over 300m of OM3 cable or 2.9dB over 400m of OM4 cable.
 
Conclusion
fiber-mart.com offers you a wide variety of 40GBASE-SR4 QSFP+ transceivers for your high-density and low-power 40 Gigabit Ethernet connectivity options branded by many famous companies like Cisco, Juniper or HP. And we also provide other compatible 40G QSFP+ transceivers, such as 40GBASE-LR4 QSFP+ transceiver, 40GBASE-ER4 QSFP+ transceiver, 40GBASE-CSR4 QSFP+ transceiver, etc. Every fiber optic transceiver provided by fiber-mart.com has been tested to ensure its compatibility and interoperability. You can buy from us with confidence.

How to choose the right Armored Fiber Patch Cable

Fiber optic jumper cables, as one of the most common component in fiber optic networks, are a transmission medium used to transmit data via light. There are many types of fiber optic jumper cables. For example, by fiber optic cable types, there are single mode patch cable and multimode patch cord; by optical connector, there are ST ST fiber patch cable, LC SC fiber patch cable, and so on; and by fiber optic cable jacket, there are PVC and LSZH fiber patch cords. And you can even order custom fiber patch cables with custom lengths and colors. In this post, a type of fiber patch cord, armored fiber patch cable, will be introduced.
 
Structure
The outer sleeve of armored fiber patch cable is usually made of plastics, like polyethylene, to protect it against solvents and abrasions. The layer between sleeve and inner jacket is an armored layer made of materials that are quite difficult to cut, chew and burn. Besides, this kind of material is able to prevent armored fiber patch cable from being stretched during cable installation. Ripcords are usually provided directly under the armored and the inner sleeve to aid in stripping the layer for splicing the cable to connectors or terminators. And the inner jacket is a protective and flame retardant material to support the inner fiber cable bundle. The inner fiber cable bundle often includes structures to support the fibers inside, like fillers and strength members. Among them, there is usually a central strength member to support the whole fiber cable.
 
Features
Armored fiber patch cable, as a member of fiber optic jumper cables family, it retains all the features of standard fiber patch cables. Compared with those common patch cables, armored fiber patch cables are much stronger and tougher. For example, once stepped by an adult, standard patch cables may get damaged easily and fail to work normally. But armored fiber patch cables can withstand the pressure and perform well. Armored fiber patch cables are rodent-resistant, which means that you don't need to worry about rats biting the cables.
 
Basically, armored fiber patch cables offer benefits and features of traditional fiber patch cables, but they are with the production and durability of armor. Armored fiber patch cables allow high flexibility without causing damage, which proves to be helpful especially in limited space. Moreover, armored fiber patch cables offer an ideal option for harsh environments without adding extra protection. Apparently, they provide an efficient solution for many fiber cable problems such as twist, pressure and rodent damage.
 
Types
There are mainly two types of armored fiber patch cable, indoor armored fiber patch cable and outdoor armored fiber patch cable.
 
Indoor armored fiber patch cable is used for indoor applications. It consists of tight-buffered or loose-buffered optical fibers, strength members and an inner jacket. The inner jacket is commonly surrounded by a spirally wrapped interlocking metal tap armor. As the fiber optic communication technology develops rapidly with the trend of FTTX, there is a fast growing demand for installing indoor fiber optic cables between and inside buildings. Indoor fiber patch cable experiences less temperature and mechanical stress. Besides, it can retard fire effectively, which means it only emits a low level of smoke in the face of fire.
 
Outdoor armored fiber patch cable is designed to ensure operation safety of the fiber in complicated outdoor environments. Most outdoor armored fiber patch cables are loose buffer design, with the strength member in the middle of the whole cable, loose tubes surrounding the central strength member. Inside the loose tube there are waterproof gels filled, the whole cable materials and gels inside the cable between different components (not only inside the loose tube) help make the whole cable resist water. The combination of the outer jacket and the armor protects the fibers from gnawing animals and damages that occur during direct burial installations.
 
Applications
Armored fiber patch cable is generally adopted in direct buried outside plant applications where a rugged cable is needed for rodent resistance. It has metal armor between two jackets to prevent from rodent penetration. Armored fiber patch cables can withstand crush loads well. Another application of armored fiber patch cable is in data centers, in which cables are installed under the floor where it can be easily crushed. Single or double armored fiber patch cable is typically used underwater near shores and shoals. And armored fiber patch cords are also used in customer premises, central offices and in indoor harsh environments. They can provide flexible interconnection to active equipment, passive optical devices and cross-connects.
 
Conclusion
In summary, when transmitting data or conducting power in harsh environments, protecting your cables is crucial to safe and reliable operation. This is where armored fiber patch cables come into play. Armored fiber patch cables are used in applications where cables will be exposed to mechanical or environmental damage under normal operating conditions.

Are You Ready for Using 40G and 100G transceivers?

Data centers regularly undertake their own great migration, to ever higher speed networks. 10G, unimaginable a decade ago, is now common in larger enterprises. And now many enterprises have to adopt 40 Gigabit Ethernet or even 100G in the aggregation and core layers of data center networks in order to meet the overall bandwidth demands of top-of-rack servers. The need is clear: a 40/100G Ethernet migration plan is quickly becoming a matter of survival. Is your network cabling optimized for this inevitable growth? Are you ready for 40G and 100G?
 
Fiber Transmissions at Higher Speeds
When moving to 40/100GbE, the most important difference in backbone and horizontal multimode applications is the number of fiber strands. 40GBASE-SR4 uses 8 strands in total, 4 strands to transmit and 4 to receive. 100GBASE-SR10 uses 10 lanes to transmit and another 10 lanes to receive for a total of 20 strands. In data centers and backbones, it may be possible to have 8 or 20 individual strands of fiber. However, those strands may take disparate paths from one end to the other and this can cause delay skew (known as bit skew) resulting in bit errors. For this reason, the 40/100GbE standards are written around fiber optic trunk assemblies that utilize a MPO/MTP multi-fiber array connector. Data is transmitted and received simultaneously on MTP interfaces through 10G simplex transmission over each individual strand of the array cable. In these assemblies, all strands are the same length. Also referred to as "parallel optics", this construction minimizes bit/delay skew, allowing the receive modules to receive each fibers information at virtually the same time.
 
Copper Transmissions at Higher Speeds
The first 10GbE capable copper interface was developed for the 10GBASE-CX4 application. The physical requirements for this shielded four-lane copper connector is standardized under SFF-8470. As a passive assembly, the SFF-8470/CX4 cables have a reach of 15m. This assembly supports 10GbE, InfiniBand, FibreChannel and FCoE. These assemblies use twinax cable, constructed of two inner conductors with an overall foil covered by a braid shield. Due to their low latency, these cables are popular in supercomputing clusters, High Performance Computing and storage. As part of the 802.3ba 40/100GbE standard, multi-lane 40GBASE-CR4 and 100GBASE-CR10 was defined. This standard specifies the use of 4 and 10-lane twinax assemblies to achieve 40 and 100GbE speeds for distances up to 7m.
 
40/100G MPO/MTP System
MPO/MTP is available in both 12 and 24 strand termination configurations used at the end of a trunk assembly. A modular laser optimized multimode MPO/MTP system that supports 40G and 100G fiber optic networks includes trunks, harnesses, array cords, modules, and adapter plates. For 40GbE, a 12-fiber cabling solution with each channel featuring four dedicated transmit fibers and four dedicated receiver fibers is used. In general, the middle four fiber remain unused. Parallel transmission is also used for 100GbE with a 24-fiber solution or two 12-fiber solution.
 
At present, 40GbE is taking over from 10GbE as the new high-growth market segment. Meanwhile, the 40GbE optics are universal in data center and the market of 100GbE is accelerating. Being prepared for 40/100G is essential: within a few short years higher-speed Ethernet will be common in data centers across all types of organizations. fiber-mart.com is ready. fiber-mart.com offers various optical communication products to meet diverse demands. For example, we provide 40GBASE-SR4 QSFP+ transceivers, like Finisar FTL410QE2C 40GBASE-SR4 QSFP+ transceiver and Mellanox MC2210411-SR4 40GBASE-SR4 QSFP+ transceiver, which are branded by famous companies and quality guaranteed.

2019年8月13日星期二

Six Basic Procedures for Fiber Cable Testing

Customers for fiber optic cable installations usually require documentation of test results before accepting and paying for the work. Testing needs to be done carefully to ensure the measurements are accurate and reliable. A definitive repertoire of tests, known as the "essential six," can benefit the inexperienced system engineer. Six basic test procedures measure distance, fiber loss, event loss, link loss, event-return loss and link-return loss. These procedures are implemented at all four levels of fiber operation, including pre-installation, installation and acceptance, maintenance and restoration.
 
An OTDR can be used to accomplish the six test procedures. In addition, clean connections on the fiber media under test are imperative. All six test procedures will prove inaccurate or impossible to accomplish if the fiber-optic connectors are dirty.
 
Distance Testing
The optical distance between one point and another depends on definition. For example, the distance could be the fiber-cable length between a transmitter and a receiver, or it could be the fiber-cable length between two splices. An OTDR is the test instrument used worldwide to measure optical test events either automatically or manually. Events are detected as disturbances in the OTDR's relatively linear trace display.
 
To measure optical distance between two points, the OTDR launches a laser-generated light pulse down the fiber at the transmission end of the cable. The instrument then detects the backscatter returned from the fiber and any reflections from shiny surfaces. It measures the time taken by the light pulse to make the round trip on the fiber and calculates that time into distance.
 
One minor deviation in this test is the difference between real and apparent distance. The optical, or apparent distance, is the distance reading registered on the OTDR, and is always longer than the real distance. One reason for the distance difference results from the undulation of fiber as it resides within loose-tube cable, which adds to its length. Another reason involves buried cable as it winds within a trench, thereby producing a longer optical length.
 
Fiber-loss Testing
The backscatter trace is a representation of the fiber itself. The slope of the backscatter trace discloses that less and less light is being reflected back as the length of the fiber increases. This slope represents fiber loss, a manufacturer's specification. Typical fiber-loss measurements are given as the amount of light (in decibels) lost per kilometer. For example, a long-haul telephone fiber might lose 0.15 dB/km, whereas a multimode local area network fiber could lose 3 dB/km. Fiber loss is always measured along a featureless section of backscatter with no events to skew the calculation.
 
Event Loss Testing
A test event is a disturbance that occurs above or below the backscatter baseline. Splices, connectors, bends and cracks are typical events that produce trace disturbances on the OTDR display. Normally (but not always), an event results in a loss of light. There are two types of events--reflective and non-reflective. The spikes along the baseline indicate a reflection. Because more photons appear and thus exceed the normal backscatter level, a mechanical splice or the end of the fiber is revealed. Other causes of reflections are connectors and fiber cracks.
 
Events that occur along the fiber become important when a fiber-loss budget is calculated. Only a finite amount of light is launched by the transmitter. Consequently, if the receiver does not receive enough light, a major cable problem has occurred.
 
Link Loss Testing
Link loss is the total amount of light lost between two points. A link can be the distance between events or between two end points. Total link loss is typically specified when it directly affects the loss budget. If the link loss is a high value, then specific events are consuming light.
 
Return Loss Testing
Return loss is essentially the light lost because of reflections back toward the transmission or source end. The shiny surfaces of connectors and mechanical splices reflect light. Some of this reflected light returns to the source. Any transmitted light that does not reach the end of the fiber is lost. An OTDR trace displays return loss as the height of a reflection.
 
Return loss is defined as the ratio in dB of the incident power to the reflected power. Return loss is always expressed as a positive number:
 
In contrast, reflectance is defined as the ratio of reflected power to the incident power or the inverse of the return-loss formula. When expressed in decibels, reflectance is a negative number. In addition, reflectance can be expressed in terms of density or as a percentage.
 
In reality, these terms mean noise. The reflected light travels back to the source, reflects off the input and makes another round trip. To a digital system, the reflected light looks like a bit error. To an analog system, such as cable TV, reflected light creates sparkle. The higher the reflection value, the more dramatic the noise level becomes.
 
Link-return Loss Testing
Link-return loss is similar to link loss. It is the total amount of reflected light in the link. Therefore, link-return loss is often used as an acceptance test. If the total amount of return loss is below a certain level, the link is assumed not to contain a single event reflecting above specification.
 
Conclusion
These six essential tests should be used to test fiber during pre-installation, installation and acceptance, and for maintenance andrestoration. A pre-installation test should be performed when fiber-optic cable arrives from the vendor. This receiving type of test is important because it quickly and easily determines product acceptance or rejection before system usage.