2018年12月9日星期日

How to Select the Right Fiber Patch Cable for 40G QSFP+ Transceiver?

by www.fiber-mart.com
As the quest for greater bandwidth continues and fibre optic connections within data centres and optic fibre networks increase, these challenges must be met by choosing the right type of connectivity. This is all driven by requirements for additional switching and routing, storage, virtualization, convergence, video-on-demand (VoD) and high performance cloud computing. All of these applications plus other bandwidth intensive applications increase the need for transmission speed and data volume over short distances.
 
Optic fibre 10G transmission systems are becoming more widely used and accepted and migration paths to 40G and 100G have been specified for optical fibre.
 
The IEEE 802.3ba 40G / 100G Ethernet standard provides guidance for 40G / 100G transmission with multimode fibre. OM3 and OM4 are the only multimode fibres included in the standard.
 
Parallel optics technology has become the transmission option of choice in many data centres and labs as it is able to support 10G, 40G, and 100G transmission. For parallel optics to work effectively, it requires the right choice of cable and connector.
 
Parallel optic interfaces differ from traditional fiber optic communication in that data is simultaneously transmitted and received over multiple optical fibres. In traditional (serial) optical communication, a transceiver on each end of the link contains one transmitter and one receiver. For example, on a duplex channel the transmitter on End A communicates with the receiver on End B and another optic fibre is connected between the transmitter on End B and the receiver on End A.
 
In parallel optical communication, the devices on either end of the link contain multiple transmitters and receivers, e.g. four transmitters on End A communicate with four receivers on End B. This spreads the data stream over the four optical fibres. This configuration would allow for the operation of a parallel optics transceiver which uses four 2.5 Gb/s transmitters to send one 10 Gb/s signal from A to B. In essence, parallel optical communication is using multiple paths to transmit a signal at a greater data rate than the individual electronics can support. This type of connectivity utilises a ribbon cable type design with all fibres aligned in a straight array, in either a 12 fibre or 24 fibre configuration.
 
In addition to the cable performance, the choice of physical connection interface is also important. Since parallel-optics technology requires data transmission across multiple fibres simultaneously, a multifibre connector is required. Factory terminated MPO / MTP connectors which have either 12 fibre or 24 fibre array, will support this solution. For example, a 10G system would utilise a single MPO / MTP (12 Fibre) connector between the 2 switches. Modules are placed on the end of the MPO connector to transition from a MPO connector to a 12 Fibre breakout LC duplex or SC duplex cable assembly. This enables connectivity to the switch. 40G and 100G systems require a slightly different configuration.
 
Utilising MPO / MTP connectivity has many benefits including:
 
High Density – multifibre connector and compact dimension of cable save space in costly data centre environments.
Reduces cable load in raised floors to existing active server/switch/storage equipment with LC Duplex interface (less cable OD, less connections.
 
Pre-connectorised solution, no splicing required on site.
Reliability -100% tested factory tested in a controlled environment
Latest active equipment by Cisco / IBM / HP /Sun Microsystems has the MPO-SFP connectivity interface for Gigabit Network transmission
Rapid Deployment – factory terminated modular system saves installation and reconfiguration time during moves, ads and changes.
Next Generation Network Proof – emerging high speed protocol are going to use MTP interface- your cabling infrastructure remains unchanged.
 
Difference between MPO and MTP connectors
From the outside there is very little noticeable difference between MPO and MTP connectors. Infact, they are completely compatible and inter-mateable. For example, an MTP trunk cable can plug into an MPO outlet and vice versa.
 
The main difference is in relation to its optical and mechanical performance. MTP is a registered trademark and design of UsConnec, and provides some advantages over a generic MPO connector. Since MPO / MTP optic fibre alignment is critical to ensure a precise connection there are some benefits in utilising the MTP connector. The MTP connector is a high performance MPO connector with multiple engineered product enhancements to improve optical and mechanical performance when compared to generic MPO connectors.
 
The MTP optic fibre connector has floating internal ferrule which allows two mated ferrules to maintain contact while under load. In addition, The MTP connector spring design maximizes ribbon clearance for twelve fibre and multifibre ribbon applications to prevent fibre damage.
 
Overall it provides a more reliable and precise connection.
 
In addition, it is also important when specifying an MPO/MTP system to ensure the correct polarity options and which cables and outlets have female or male pins.
 
In conclusion, three main factors must be considered are fiber optic cable type, fiber optic connector type and the switch port. In practical cabling, more should be considered. These three aspects are far from enough.

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