Optical Receiver Mitigating Chromatic Dispersion Nulls
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Long-haul optical transmission systems face limitations in signal recovery due to chromatic dispersion, as intensity modulation and direct detection systems fail to preserve phase information, leading to deep nulls in the received signal spectrum, making it incompatible with electronic dispersion compensation techniques.
Innovation Solution
A receiver apparatus with an optical splitter and multiple optical detectors, each with a frequency-dependent phase shifter, generates multiple electrical signals that are combined by an electronic processor to recover information from the optical signal, mitigating the effects of chromatic dispersion by ensuring nulls occur at different frequencies, thus enabling the recovery of all portions of the electrical signal spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If intensity modulation and direct detection are used in optical transmission systems, then system simplicity and cost-effectiveness are improved, but phase information is lost leading to deep nulls in the received signal spectrum
Solution Approach 1:
The received optical signal is divided into multiple copies and distributed to separate detection paths. Each path applies a different frequency-dependent phase shift before detection, allowing the system to process different spectral components independently and combine them to recover information that would otherwise be lost in any single path.
Solution Approach 2:
The invention transitions from single-dimensional direct detection to multi-dimensional processing by introducing frequency-dependent phase shifts as an additional dimension. This allows the system to access and process phase information indirectly through multiple phase-shifted copies of the signal, effectively adding a new degree of freedom to the detection process.
2Reliability
If dispersion compensating fibre is used to compensate chromatic dispersion, then signal quality is improved, but additional attenuation and non-linear properties are introduced
Solution Approach 1:
The invention replaces the optical-domain dispersion compensation mechanism (dispersion compensating fibre) with an electronic-domain processing approach. By applying frequency-dependent phase shifts electronically after detection, the system achieves dispersion compensation without introducing the additional optical attenuation and non-linear effects that would result from adding more optical fibre.
3Reliability
If fixed optical equalisation means are used for dispersion compensation, then chromatic dispersion is compensated, but flexibility and reconfigurability are limited
Solution Approach 1:
The invention employs dynamically adjustable phase shifters that can be reconfigured to apply different frequency-dependent phase shifts based on the specific dispersion conditions. This allows the system to adapt to changing transmission conditions, wavelengths, and dispersion characteristics, providing the flexibility and reconfigurability that fixed optical equalisation means lack.
4Loss of information
If multiple optical detectors with frequency-dependent phase shifters are used, then spectral nulls are mitigated and information recovery is improved, but device complexity increases
Solution Approach 1:
The invention combines multiple detection paths with different phase shifts into a unified processing architecture. By coherently combining the outputs of multiple detectors through electronic processing, the system achieves improved information recovery and mitigation of spectral nulls while managing the complexity through integrated design rather than treating each detector path as a completely separate system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for improved accuracy and reliability in recovering information from dispersive optical channels, even in systems with changing dispersion conditions, by effectively combining electrical signals to overcome spectral nulls and maintain signal quality across the optical and electrical domains.
Implementation Method 1
an optical splitter having an input port arranged to receive the received optical signal and a plurality of output ports, wherein a proportion of optical power at the input port is transmitted to each said output port
Implementation Method 2
one or more optical phase shifters, each being disposed between an output port of the optical splitter and a respective one of said optical detectors, wherein the or each optical phase shifter applies a frequency-dependent phase shift to an optical signal passing therethrough
Implementation Method 3
a plurality of optical detectors operably connected to respective output ports of the optical splitter, for generating a corresponding plurality of electrical signals
Data Source
AI summary
A receiver for recovering transmitted information carried by a received optical signal that has been affected by dispersion includes an optical splitter having an input port arranged to receive the received optical signal, and a plurality of output ports. A proportion of optical power at the input port is transmitted to each of the output ports. A plurality of optical detectors is operably connected to respective output ports of the optical splitter, for generating a corresponding plurality of electrical signals. Optical phase shifters are disposed between the output ports of the optical splitter and respective optical detectors. As a result, each optical phase shifter applies a frequency dependent phase shift to an optical signal passing therethrough. An electronic processor includes analog and/or digital electronic components configured to combine two or more of the plurality of electrical signals, or information recovered separately therefrom, in order to provide improved accuracy or reliability of information recovery as compared with detecting and processing only the received optical signal. The receiver is advantageously able to mitigate the effects of frequency-dependent fading which may occur in intensity modulation/direct detection optical transmission systems due to dispersion in optical transmission paths.