Optical Domain Equalization for Coherent Receiver Bandwidth
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Solution Overview
Problem
High-speed optical receivers face challenges in maintaining low noise levels and sensitivity, especially when dealing with high data rates and bandwidth limitations in optical communication systems, which limits their ability to transmit signals over long distances with minimal loss.
Innovation Solution
The optical coherent receiver incorporates an optical domain equalizer that compensates for bandwidth limitations by using an optical hybrid with phase-shifted and delayed light signals, coupled through tunable splitters and attenuators to enhance high-frequency components, effectively increasing the receiver's bandwidth and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the receiver operates at high data rates, then the transmission speed increases, but the noise level increases and sensitivity decreases
Solution Approach 1:
The optical signal is split into multiple paths with different time delays using optical splitters and delay elements. Each path processes the signal independently and then they are combined, allowing the system to maintain high data rate performance while reducing noise through diverse signal paths
Solution Approach 2:
An optical equalizer network is introduced as an intermediary component between the optical hybrid and the photodetectors. This equalizer network compensates for bandwidth limitations and noise characteristics, enabling high-speed operation with reduced noise impact
2Device complexity
If the receiver bandwidth is limited, then the device complexity is reduced, but the transmission distance and loss tolerance decrease
Solution Approach 1:
The optical equalizer network performs preliminary signal conditioning and compensation for bandwidth limitations before the signal reaches the photodetectors. By pre-equalizing the signal in the optical domain, the system can achieve extended bandwidth performance without proportionally increasing receiver complexity
Solution Approach 2:
The patent replaces electrical domain equalization with optical domain equalization. By performing signal processing in the optical domain using passive optical components rather than active electrical components, the system achieves extended bandwidth with lower complexity and reduced noise
3Length of stationary object
If optical loss in the receiver-transmitter path increases, then the transmission distance increases, but the receiver sensitivity decreases
Solution Approach 1:
The optical equalizer network continuously processes the signal across multiple time-delayed paths, maintaining signal integrity and strength throughout the transmission path. This continuous optical processing helps compensate for optical loss and maintains receiver sensitivity over extended transmission distances
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 configuration enhances the receiver's sensitivity and extends its bandwidth, enabling it to handle higher data rates with lower noise levels, thus improving the transmission of signals over longer distances with greater optical loss tolerance.
Implementation Method 1
the OH may be configured to direct light received in the first input OH port and light received in the second input OH ports into each of the first and second output OH ports with a relative phase shift that increments by 180° from the first output OH ports to the second output OH port
Implementation Method 2
the optical equalizer network may be configured so that in operation light received at each of the first and second back-end optical ports from one of the first and second output OH ports is delayed by a time delay τ relative to light received from the other of the first and second output OH ports
Implementation Method 3
the receiver may comprise a first optical splitter optically coupled to the first output OH port for splitting light received therefrom between the first and second optical back-end ports, and a second optical splitter optically coupled to the second output OH port for splitting light received therefrom between the first and second optical back-end ports
Data Source
AI summary
An optical coherent receiver includes an optical hybrid (OH) configured to mix signal and reference light, and two back-end optical ports. An optical equalizing network interconnects two 180° OH output ports with the two back-end optical ports so that each back-end optical port receives light from each of the two OH output ports. Optical signals from each of the two back-end optical ports are converted to electrical signals that are fed to a differential amplifier. Adjusting coupling ratios and/or optical delays in the optical equalizing network reduces an OSNR penalty of a lower-bandwidth differential amplifier.