CA2453012A1 - Control of tunable optical dispersion compensation by electronic dispersion compensator - Google Patents

Description

Preliminary DISCLOSURE OF INVENTION
Disclosure Number DI: DI 031032 Date Received:
Received by: Melanie Budarick Patent Committee Use Inventor's Section A. Administrative:
Title of Invention Control of Tunable Optical Dispersion Compensation by Electronic Dispersion Compensator Inventor(s):
Name Signature Identify InventiveDate and Location Contribution of First Record Arthur G. Inventor Wilson Please ensure each inventor Fisted above completes the attached information nape.
Any delay in providing this information will cause a delay in awarding a stock option award for a conventional US patent application, where applicable.
B. Has any publication or disclosure to others been made, or has there been any sale or delivery of prototypes?
Yes 0 No Details of prior This invention was accidentally disclosed to personnel from Aegis disclosure: Semiconductor (optical dispersion compensator potential source) during a conference call, though it was not identified as potential IP. Aegis did agree that this was the most logical way to control such a device cost effectively and presented the idea back to JDSU is a subsequent confidential briefing.
C. Description Answer all the following. (May be included with additional sheets) i. In one sentence, what is the invention?
Utilizing both electronic and optical dispersion compensation within an optical transceiver or transponder module with the optical compensator setpoint driven by metrics generated by the electronic compensator.
LIST three to five (3 to 5) keywords that describe your invention.
Adaptive, receiver, "dispersion compensator"
DESCRLBE THE INVENTION IN DETAIL. Completeness is essential. Note that the description given may be filed directly without editing in order to establish priority. Use extra sheets as necessary. The disclosure should be understandable by a non-specialist technical person. Diagrams are usually necessary to explain an invention adequately.
This invention relates to 1 OG transponderltransceiver configurations which are intended for use in amplified systems at greater than 80 km, with a goal of at least the size of a typical metro ring, 240 km. This invention ma also be a lied to 40G transponders/transceivers at distances of one Rev August 12, 2002 Page 1 Preliminary DISCLOSURE OF INVENTION
sixteenth those stated for 1 OG. Carriers wish to be able to upgrade existing

2.5G rings to 10G
without the task and expense of engineering, procuring, and installing passive dispersion compensation modules (typically packaged lengths of dispersion compensating fiber) in the transmission path. The logical approach is to integrate such compensation into the optical interface modules themselves.
Figure 1 compares the typical transponder (or transceiver, without the electrical demux function) implementation with the improved approach described herein. Traditionally, the optical signal is converted into an analog electrical signal by the photoreceiver, which may be APD or PIN detector based. The output of the photoreceiver may be further processed by a postamplifier or clock and data recovery circuit, which makes the received analog signal compatible with following circuitry.
The following circuitry may be an electrical demultiplexer as shown for transponder applications, or the signal may exit the optical module at the Postamp output in transceiver applications.
The improved approach adds an electrical adaptive filtering block (commonly called EDC for electronic dispersion compensation) and an adjustable optical dispersion compensator. The EDC
block is now beginning to be implemented in transponders and transceivers, yet current generation EDC implementations only increase dispersion tolerance of the optical interface by approximately 50%. An 80 km interface then may be extended to 120 km, insufficient to achieve a full ring reach of 240 km. The control of the EDC block (filter tap weight calculation) is normally achieved by calculating quality metrics of the filtered eye, then optimizing those metrics through an associated controller running an algorithm (example: least mean square error) which modifies the weights to maximize eye quality.
It is not a stretch to extend the dispersion tolerance by adding an adjustable optical dispersion compensator in the optical path before the receiver: Normally, this block would require manual adjustment using equipment external to the optical interface module (BER
feedback, optical eye monitoring, etc.). This compensator could be bragg grating, etalon, or all pass filter waveguide filter based. The invention is in automatically controlling the setpoint of the ODC block with the eye metrics developed by the EDC device, thereby extending the dispersion tolerance optimization range of the transponder/transceiver. It is expected that this approach may be used to extend the useful communication range of the transponderltransceiver to beyond 500 km without expensive dispersion compensator modules in the network, thereby reducing carrier capex (equipment costs) and opex (cost to engineer, install, and tweak the DCMs and added optical amplification required to overcome the losses in the DCMs) needed to upgrade existing rings to 10 Gbls. This approach is also valuable in a reconfigurable optical network, where the path may not be known a priori, and the combined approach allows the transponderltransceiver to optimize the path in real time after a path switch. The concept may be also be extended to control of adaptive PMD compensators, where historically the feedback for the control loop uses expensive and large optical PMD sensing. This would be particularly valuable in 40 Gbls interfaces.
iv. Describe the prior art Previous implementations of dispersion compensation have typically been optically based, with either fixed, "set and forget' (non adaptive), or adaptive functionality based on feedback from direct measurements of the transmission path's optical chromatic dispersion or statistics of errored bits as determined by the receiver's FEC decoder if present. Non adaptive solutions cannot compensate for changes in' chromatic dispersion due to a reconfigurable network's changes in path length. Optical measurements are expensive and difficult to implement within shrinking transponderltransceiver physical envelopes, and FEC decoders are not normally accepted by the market as part of a transceiver or transponder.
Rev August 12,2002 Page 2 Preliminary DISCLOSURE OF INVENTION
v. Identify what aspects of the invention need to be protected. Remember that the purpose of a patent is to PREVENT OTHERS from doing something.
The aspect of controlling a tunable optical dispersion compensation device by the metrics developed to control an electronic,dispersion compensator IC which is also within the optical transceiver/transponder module. Customers are already looking at using EDC to help guarantee interoperability at 80 km, and JDSIJ has evaluated concepts and prototypes of transponders which achieve extended reaches (200-500 km) by integrating tunable dispersion compensation in the optical domain. The adaptive approaches have relied on external error rate feedback to train and optimize the ODC setpoint.
vi. What is the status of the invention at JDSU? (May range from "in production" to "concept only') Concept only at this time, awaiting the development of ODC subassemblies which are cost effective for single channel usage within a transponderltransceiver. The EDC
ICs are in evaluation at JDSU. Overall concept likely to be implemented on JDSU LH
transponders to achieve optimized BER performance at distances to 500+ km at 10 Gbls.
D. Dated at Melbourne, FL this day of Arthur G. Wilson Signature of Originator Print name Read and understood by:
Witness (Print Name) Signature of Witness Date Management Section Manager'slBusiness Unit Comments I have renewed this submission and agree it presents novel approaches central to protecting our ongoing work in dispersion compensating component, module & system designs. I
fully support this DI and advocate a patent filing. Ron Genova - VP Telecom BU
Rev August 12, 2002 Page 3

Claims

Claims An dispersion compensation receiver comprising:
a compensation component for optical dispersion compensation;
a detector for receiving a optical signal from the compensation component electronic circuitry for detecting an eye pattern from an electrical signal received from the detector;
processing means for analyzing eye pattern metrics of the eye pattern and for controlling the compensation component.