Spectrally Interleaved Optical Transceivers for Bidirectional WDM
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Solution Overview
Problem
Conventional optical transceivers face limitations in achieving fast, bidirectional communication due to the limited free spectral range (FSR) of on-chip resonant modulators, which restricts the number of WDM channels and leads to interference between signals traveling in opposite directions.
Innovation Solution
The transceiver is designed with separate transmit and receive bus waveguides and employs an optical interleaver, such as an asymmetric Mach Zehnder interferometer, to selectively couple wavelengths, preventing interference by using π-shifted spectral responses and phase shifters to minimize cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If on-chip resonant modulators are used for WDM transmission, then wavelength selectivity is improved, but the free spectral range is limited which restricts the number of WDM channels
Solution Approach 1:
The patent divides the single resonant modulator into multiple independent resonant modulators, each tuned to a different wavelength within the limited FSR. This segmentation allows multiple WDM channels to be transmitted simultaneously by using multiple resonant elements instead of one, thereby increasing the number of channels without requiring a larger FSR.
Solution Approach 2:
The patent combines multiple resonant modulators operating at different wavelengths into a single integrated optical device. By merging multiple wavelength-selective elements that each operate within the available FSR, the system achieves multi-channel WDM capability while maintaining the benefits of on-chip integration and compact form factor.
2Productivity
If bidirectional communication is implemented using the same optical channel, then resource utilization is improved, but signal interference occurs between opposite-direction signals
Solution Approach 1:
The patent employs asymmetric Mach-Zehnder interferometers with different path length differences in each arm, creating π-shifted spectral responses for forward and reverse directions. This asymmetry ensures that wavelengths selected for transmission in one direction are rejected in the opposite direction, eliminating cross-talk while allowing bidirectional communication over the same optical channel.
Solution Approach 2:
The patent introduces an optical interleaver as an intermediary component that mediates between the resonant modulators and the optical channel. This interleaver separates the spectral content for different directions by using π-shifted responses, allowing bidirectional signals to coexist on the same channel without interference.
3Productivity
If the number of WDM channels is increased to improve data capacity, then bandwidth utilization is improved, but cross-talk between channels increases
Solution Approach 1:
The patent assigns different local spectral characteristics to different wavelength channels through the use of π-shifted MZIs. Each wavelength channel is selectively coupled with specific path length differences that create localized spectral filtering, ensuring that channels are well-separated in the spectral domain and minimizing cross-talk even as the number of channels increases.
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 design allows for twice the number of WDM channels in the same spectral band without increasing FSR, enabling efficient, interference-free bidirectional communication.
Implementation Method 1
an optical interleaver configured to: selectively couple light having carrier wavelengths in the first wavelength set from the first waveguide bus to the I/O port, and selectively couple light having carrier wavelengths in the second wavelength set from the I/O port to the second bus waveguide
Implementation Method 2
the optical interleaver comprises a Mach Zehnder interferometer (MZI) having a first coupler coupled to both the first and second bus waveguides and a second coupler coupled to the I/O port
Implementation Method 3
the first stage of the multi-stage MZI defines a first optical path length difference and the second stage of the multi-stage MZI defines a second optical path length difference different from the first optical path length difference
Implementation Method 4
When multiple wavelengths of light are introduced into a waveguide, a ring resonator selectively couples the wavelength that matches its resonant wavelength
Data Source
AI summary
Described herein are wavelength division multiplexing (WDM) transceivers configured to support fast, bidirectional communication over optical channels. An optical transceiver comprises a transmitter, a receiver, an input/output (I/O) port and an optical interleaver. The transmitter comprises a first bus waveguide and a plurality of optical modulators coupled to the first bus waveguide, each of the optical modulators being resonant at a respective wavelengths in a first wavelength set. The receiver comprises a second bus waveguide and a plurality of optical filters coupled to the second bus waveguide, each of the optical filters being resonant at a respective wavelength in a second wavelength set. The (I/O) port is coupled to an optical channel. The optical interleaver is configured to selectively couple light having wavelengths in the first wavelength set from the first waveguide bus to the I/O port, and selectively couple light having wavelengths in the second wavelength set from the I/O port to the second bus waveguide.