Bi-Directional Optical Link Dispersion Pre-Compensation With Adaptive Filters
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Solution Overview
Problem
Conventional methods for chromatic dispersion pre-compensation in bi-directional optical links are cumbersome, costly, and inefficient, leading to improper adaptation and synchronization issues between transceivers, requiring additional infrastructure and complex processes.
Innovation Solution
A method and transceivers that generate chromatic dispersion pre-compensated optical signals using CD pre-compensation filters, allowing transceivers to adapt CD pre-compensation without prior knowledge of link conditions, enabling accurate and tunable compensation without additional channels or complex recovery systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dispersion compensating fiber is used to compensate chromatic dispersion, then chromatic dispersion compensation is achieved, but the system becomes bulky, expensive, and introduces substantial attenuation and nonlinear impairments
Solution Approach 1:
The patent replaces the mechanical/optical dispersion compensating fiber system with an electrical digital signal processing system. Specifically, it uses digital filters (FIR or IIR) implemented in field-programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs) to perform chromatic dispersion compensation through electrical means rather than optical means, thereby eliminating the need for bulky DCF components and their associated problems.
Solution Approach 2:
The patent changes the parameter of compensation timing from post-compensation (after optical transmission) to pre-compensation (before optical transmission). By applying digital filters at the transmitter to pre-distort the signal in opposition to expected chromatic dispersion effects, the system achieves compensation without requiring complex optical compensation components at the receiver.
2Reliability
If optical means such as fiber Bragg gratings are used for CD compensation, then chromatic dispersion compensation is achieved, but the devices are bulky, expensive, and degrade the optical signal due to inadequate response
Solution Approach 1:
The patent substitutes optical compensation devices (fiber Bragg gratings, etalons, VIPAs) with electrical digital signal processing systems implemented in programmable logic devices. This replacement eliminates the need for precise optical alignment, bulky optical components, and expensive manufacturing processes associated with optical means.
Solution Approach 2:
The patent implements dynamically adjustable digital filters that can be reconfigured through software or firmware updates. The filter coefficients can be adapted to different transmission conditions, distances, and signal rates, providing flexibility that fixed optical compensation devices cannot match.
3Ease of operation
If conventional transceivers without correct CD pre-compensation are used in bidirectional optical links, then bootstrapping is enabled, but the transceivers cannot synchronize and proper communication cannot be established
Solution Approach 1:
The patent applies preliminary chromatic dispersion pre-compensation to the optical signal before transmission. By pre-distorting the signal at the transmitter using digital filters, the signal arrives at the receiver already compensated for chromatic dispersion effects, enabling successful synchronization and communication establishment during the bootstrapping phase without requiring complex adaptive equalization.
Data Source
AI summary
A method for optical communication between transceivers through an optical link for chromatic dispersion pre-compensation, includes generating and sending, by a second transceiver, a first CD pre-compensated optical signal and a second CD pre-compensated optical signal, to the first transceiver through the optical link. The method further includes receiving, by a first transceiver, the first and second CD pre-compensated optical signals, and calculating a first residual chromatic dispersion (RCD) value from the received first CD pre-compensated optical signal, and a second RCD value from the received second CD pre-compensated optical signal. The method further includes calculating, by the first transceiver, a third PCD filter using the first RCD value, and a fourth PCD filter using the second RCD value. The third PCD filter and the fourth PCD filters are used to generate and send two CD pre-compensated optical signals to the second transceiver, which provides tunable CD pre-compensation capability.