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Fiberstore White Paper | Upgrade to High Data Rate Transmission With Parallel Optics
Parallel optics represent a type of optical communication technology as well as the devices oneither end of the link that transmit and receive information which are also known as parallel opticaltransceivers. Compared with traditional optical communication, parallel optical communicationemploys a different cabling structure for signal transmitting aiming at high-data transmission forshort reach multimode fibers that are less than 300 meters. Traditional fiber optic transceiverscannot satisfy the increasing demand for high speed transmission, like 40GbE, while parallel opticstechnology can be a cost effective solution for 40/100GbE transmission.
Comparison between parallel optics technology and the traditional serial optical communicationwould better explain what parallel optics is and the reason why it is a cost effective solution to highdata rate transmission. The following of this article will offer the comparison between the twooptical communication technology from two aspects: connectivity method and key components.
Connectivity Method
Literally, parallel optics and serial optics transmit signals in different ways. In traditional serialoptical communication, on each end of the link, there are one transmitter and one receiver. Forexample, the transmitter on End A communicates to the receiver on End B, sending a single streamof data over a single optical fiber. And a separate fiber is connected between the transmitter on EndB and the receiver on End A. In this way, a duplex channel is achieved by two fibers.
While in parallel optical communication, duplex transmission is achieved in a different way. A signalis transmitted and received through multiple paths, thus, the parallel optical communication cansupport higher data rate than the traditional optical communication. This is because, the devices for
Upgrade to High DataRate Transmission WithParallel Optics
WHITE PAPER
Fiberstore White Paper | Upgrade to High Data Rate Transmission With Parallel Optics
parallel optic communication on either end of the link contain multiple transmitters and receivers.For instance, in 2010 IEEE 802.3ba approved the 40GBASE-SR4 physical-medium-dependentmultimode parallel optical solution, which uses eight fibers to transmit four duplex channels each at10 Gigabit Ethernet. In this case, four 10Gbps transmitters on End A communicate with four 10Gbpsreceivers on End B, spreading a single stream of data over four optical fibers at a total data rate of40Gbps.
Key Components
The parallel optical communication transmitting signals over multiple fibers, which has greatadvantages over traditional serial optical communication. It also means that it requires differentcomponents to support its high data rate transmission.
Connector: As previously mentioned, duplex transmission in serial optical communication uses2-fiber duplex connectors, like duplex LC connectors to link the optics with other devices, while inparallel optical communication, multi-fibers are used to reach a higher data rate. Thus, multi-fiberconnectors, like 12-fiber MPO connectors are used to connect with other devices. MPO connector isone key technology support parallel optical communication. This connectivity method is showed inthe following picture (Tx stands for transmit; Rx stands for receive).
Optical transceiver light source: Another complementary technology for parallel transmission is thelight source of parallel optics—VCSELs (Vertical Cavity Surface Emission Lasers). Comparing with theedge-emitting semiconductor lasers in the traditional optics, VCSELs have better formed opticaloutput which enables them to couple that energy into optical fibers more efficiently. In addition,VCSELs emit from the top surface, they may be tested while they are part of a large productionbatch (wafer), before they are cut into individual devices, which dramatically lowers the cost of thelasers. The following chart is about the comparison between VCSELs and edge-emittingsemiconductor lasers. Cheaper to manufacture, easier to test, less electrical current required,supporting higher data rate, parallel optics using VCSELs could be a better choice to reach40/100GbE transmission compared with traditional serial optics.
WHITE PAPER
Fiberstore White Paper | Upgrade to High Data Rate Transmission With Parallel Optics
VCSEL vs Edge-Emitting Laser
Feature VCSEL Edge-Emitting Laser
Power consumption 2-3 mW 20 mW
Beam quality/ease of coupling Better, round low divergence Fine, asymmetric
Speed 10 Gbps 1 Gbps
Temperature stability 0.06 nm/oC 0.25 nm/oC
Specral width 1 nm 1-2 nm
Speckle Low in an array High
Parallel Optics for 40/100GbE Transmission
IEEE has already included physical layer specifications and management parameters for 40Gbps and100Gbps operation over fiber optic cable. Two popular parallel optics solutions for 40Gbps and100Gbps over multimode fibers are introduced here. For 40G, 40GBASE-SR4 transceiver is usuallyused, which requires a minimum of eight OM3/OM4 fibers for a transmit and receive link (4 fibersfor Tx and 4 fibers for Rx). 100GBASE-SR10 transceiver is for 100Gbps transmission, which requires aminimum of 20 OM3/OM4 fibers for a Tx/Rx link, 10 fibers are used for Tx and the other 10 are forRx.
Conclusion
The capabilities and uses of parallel optics and MPO technology continue to evolve and take shapeas higher-speed fiber optic transmission, including 40/100GbE. It is uncertain that parallel opticalcommunication would be the trend in the future. However, many cabling and network experts havepointed out that parallel optical communication supported with MPO technology is currently a wayto equip an environment well prepared for the 40/100GbE transmission.
WHITE PAPER
Fiberstore White Paper | Upgrade to High Data Rate Transmission With Parallel Optics
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Notice: This document is for informational purposes only and does not set forth any warranty, expressed orimplied, concerning any equipment, equipment features, or service offered or to be offered by Fiberstore.Fiberstore reserves the right to make changes to this document at any time, without notice, and assumes noresponsibility for its use. This information document describes features that may not be currently available.Contact a Fiberstore sales team for information on feature and product availability.
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