Product category:
Communications ICs (Wired)
News Release from: Phyworks | Subject: PHY1060/PHY1090/PHY1085
Edited by the Electronicstalk Editorial
Team on 15 April 2005
Chipset aims to boost bandwidth for
legacy fibre
Electronic dispersion compensation implemented in integrated circuit technology may prove to be the solution to the 10Gbit/s multimode fibre challenge.
As the density and datarate capability of networked hardware increases in enterprise local area networks (LANs), the Achilles heel preventing system upgrades in multimode fibre optical networks from the present 1Gbit/s to the required 10Gbit/s becomes apparent: the installed multimode fibre itself The primary factor limiting the reach capability of legacy multimode fibre from a few hundred metres at 1Gbit/s to a few tens of metres at 10Gbit/s is modal dispersion - the phenomenon whereby the different components of a data signal travel through multimode fibre at different speeds, and therefore arrive at the end of the fibre link at different times
This article was originally published on Electronicstalk on 1 Mar 2005 at 8.00am (UK)
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Ultimately, dispersion results in reduced timing and amplitude margin at the receiver, and hence reduced link robustness.
If future transmission bottlenecks in LANs are to be avoided, enterprise IT managers must consider the two possible solutions to this dispersion problem.
First, IT managers can specify the wholesale replacement of their installed fibre base with new higher bandwidth fibre.
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Secondly, IT managers can look to upgrading existing optoelectronic modules in their systems such that the installed fibre can be re-used.
Of these two solutions - and especially in the current low capital expenditure climate - the cost of the former is prohibitive to most enterprises, which typically only replace fibre infrastructure every 7-8 years.
As such, enterprise network managers must look towards cost effective optoelectronic module solutions to address this fundamental limitation of the installed multimode fibre.
Specifically, widespread deployment of 10Gbit/s LANs will only become a reality when optical module vendors can demonstrate a clear path to supplying datacomms equipment manufacturers with a sub-$200 pluggable optical module.
10GBase-LX4 is an optoelectronic technology that was developed several years ago to mitigate dispersive effects of multimode fibre by transmitting four optically multiplexed and encoded 3.125Gbit/s channels to deliver an aggregate 10Gbit/s.
However, this technology fundamentally excludes the possibility of cost effective high density 10Gbit/s LANs thanks to its inherent optical and mechanical complexity, and its reduced support for the smallest module form factors such as XFP.
It is clear that an alternative optoelectronic technology enabling serial 10Gbit/s networking is required to hit the sub-$200 module cost goal.
Electronic dispersion compensation (EDC) implemented in integrated circuit (IC) technology may prove to be the solution to the 10Gbit/s multimode fibre challenge; if architected correctly - and in combination other silicon innovations - EDC has the potential to help catalyse the rapid deployment of 10Gbit/s data networks.
When deployed in optical systems, EDC technology aims to compensate the dispersive effects of a fibre without training sequences or a priori knowledge of the channel, whilst simultaneously adapting to the time varying effects induced by vibrations and temperature changes.
Phyworks - a UK-based fabless semiconductor solution supplier - is spearheading the drive to solving dispersive limitations in high-speed multimode fibre LANs.
The use of EDC technology alone, however, will not solve the wider challenge of enabling a cost effective 10Gbit/s LAN solution.
And to this end Phyworks has developed a chipset with an architecture tailored to enabling the most cost compelling XFP solution.
Current XFP solutions comprise transmit and receive optical subassemblies (TOSA, ROSA), and up to five ICs including a microprocessor.
Phyworks has developed a 10Gbit/s chipset that will add EDC functionality to XFPs, while simultaneously reducing chip count and paving the way to sub-$200 1.5W XFP modules.
On the module receive side, Phyworks has developed novel EDC IC technology to mitigate the dispersion challenge.
However, a major implementation breakthrough has been to integrate the EDC function with the receive-side clock recovery IC already present in an XFP module - this is the PHY1060 device.
In addition to providing this EDC-enabled retimer, Phyworks has also developed a transimpedance amplifier for the ROSA.
The PHY1090 is a low noise TIA designed specifically for the high linearity requirements of EDC.
The TIA addresses output linearity by outputting a constant voltage swing over the entire input optical dynamic range.
In addition to receive-side IC innovations, Phyworks has also targeted the transmit chain, and offers the PHY1085 10Gbit/s laser driver with integrated retimer.
By choosing such lateral transmit- and receive-side IC integration within the module, Phyworks believes the optimal cost, power and performance tradeoffs required by module vendors can be achieved.
The use of EDC technology to enable 10Gbit/s Ethernet networks is currently under standardisation by the IEEE802.3 standards committee.
The work by the committee's 802.3aq task force - with extensive participation by Phyworks - is sufficiently advanced that a draft standard (10GBase-LRM) is expected to be published around the end of this year.
The goal of the standard is to specify robust serial 10Gbit/s links, enabling up to 300m transmission over legacy multimode fibre.
With the IC technology and architecture choices discussed, cost effective solutions to this technical and commercial challenge are a practical reality.
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