Coherent Optical Transceiver Modules for Bidirectional Single-Fiber Links
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Solution Overview
Problem
Existing optical transmission systems using coherent detection for bidirectional communication over a single fiber face challenges due to the high cost and footprint of optical coherent transceivers, as well as limitations in transmission length caused by in-band distortions, which require additional components and specific wavelength alignment.
Innovation Solution
A method and system utilizing multiple optical transceiver modules with integrated optical modulators and coherent receivers, where a multiplexed optical CW signal with differing wavelengths is used to create modulated optical signals that can be routed over the same optical path, allowing coherent detection with minimal impact on bit error ratio and OSNR performance, eliminating the need for separate lasers and optical circulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If single-fiber working is used to save installation cost, then cost is reduced, but additional optical components are required which reduces cost saving effect and transmission length is limited due to in-band distortions
Solution Approach 1:
The patent combines the local oscillator signal and transmit signal into a single optical path using wavelength division multiplexing. The local oscillator signal at wavelength λ1 and the transmit signal at wavelength λ2 are multiplexed together and transmitted through the same single fiber, eliminating the need for separate optical paths and reducing the requirement for additional optical components such as separate lasers and circulators.
Solution Approach 2:
The optical transceiver module is designed to handle multiple functions using a single optical path. The same optical fiber is used for both transmitting the modulated signal and carrying the local oscillator signal for coherent detection, making the system more versatile and reducing installation complexity while maintaining bidirectional communication capability.
2Measurement precision
If separate lasers are used for local oscillator and transmit signal, then wavelength alignment is achieved, but cost and device complexity increase
Solution Approach 1:
The patent merges the local oscillator signal generation and transmit signal generation into a single integrated optical transceiver module. Instead of using separate lasers, the module uses a single laser source that generates both signals at different wavelengths through wavelength division multiplexing, reducing component count while maintaining precise wavelength alignment for coherent detection.
3Adaptability or versatility
If optical circulators are used to separate transmission paths, then bidirectional communication is enabled, but cost and footprint increase
Solution Approach 1:
The patent combines the forward and reverse transmission paths into a single optical fiber using wavelength division multiplexing. The transmit signal at wavelength λ2 and the received signal at wavelength λ1 share the same physical fiber infrastructure, eliminating the need for optical circulators and reducing device footprint while enabling full-duplex bidirectional communication.
4Reliability
If dual-fiber working is used to avoid in-band distortions, then transmission quality is improved, but installation cost increases
Solution Approach 1:
The patent merges dual-fiber functionality into a single fiber by using wavelength division multiplexing. The local oscillator signal and transmit signal are multiplexed at different wavelengths and transmitted through the same fiber, achieving the transmission quality of dual-fiber systems while reducing installation cost by requiring only a single fiber connection.
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
Enables efficient bidirectional communication over a single fiber with reduced costs and complexity, maintaining high performance by using all optical transceiver modules and eliminating in-band distortions through appropriate filtering and signal processing.
Implementation Method 1
creating a modulated optical signal at an output port of the optical modulator
Implementation Method 2
establishing at least two bidirectional communication links using coherent detection
Data Source
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AI summary
The invention relates to a method for establishing at least two bidirectional communication links using coherent detection, the method comprising the steps of (a) providing, at each of a first and a second side of at least a first and a second optical path (106), at least two optical transceiver modules (108), wherein each optical transceiver module (108) comprises an optical modulator (110) and a coherent optical receiver (112), each optical modulator (110) having an input port, a modulation port and an output port and each coherent optical receiver (112) having a local oscillator port, a receiving port and an output port, wherein an input port (108a) of each optical transceiver module (108) is connected by an optical 1x2 power splitter device (124) to the optical modulator input port and the coherent optical receiver input port, (b) creating, at each of the first and second sides of the optical paths (106), a multiplexed optical CW signal (SCS) comprising at least two optical CW signals (SCWi) having differing wavelengths (λi), wherein the CW signals (SCWi) created at the first side and the CW signals (SCWi) created at the second side have the same or approximately the same wavelengths (λi), (c) supplying the multiplexed optical CW signal (SCW) to the input port (108a) of each optical transceiver module (108), (d) creating, at an output port of each optical modulator (110), which defines an output port of the optical transceiver module, a modulated optical signal (SMi,l; SMi,r) which includes information of one or more modulation signals (Mi,l; Mi,r) that are supplied to the modulation port of the corresponding optical modulator (110), (e) creating, at each of the first and second sides of the optical paths (106), at least two first and second optical transmit signals (STXi,l; STX,ri) by optically filtering each of the modulated optical signals (SMi,l; SMi,r) in such a way that only a single wavelength (λi) remains, and routing each at least one pair of a dedicated first and second optical transmit signal (STXi,l; STXi,r) that is used to establish the at least two bidirectional communication links to a dedicated one of the at least first and second optical paths (106), wherein the first and second optical transmit signals (STXi,l; STXi,r) of each pair have differing wavelengths (λi) and wherein the first and second optical transmit signals (STXi,l; STXi,r) that are transmitted in the same direction over the same optical paths (106) have differing wavelengths (λi), (f) routing, at each of the first and second sides of the optical paths (106), each of the at least two first and second optical transmit signals (STXi,l; STXi,r) to a receiving port of a dedicated coherent optical receiver (112), and (g) creating, at the output port of each coherent optical receiver (112), one or more electrical receive signals (SRXi,l; SRXi,r) by mixing the respective optical transmit signal (STXi,l; STXi,r) that is supplied to the receiving port and the multiplexed optical CW signal (SCW). The invention further relates to an optical transmission system (100; 200) implementing this method as well as to a multiple optical transceiver device (102, 104; 202) which is configured to be used in such an optical transmission system.