Coherent Optical Transceivers Using One Fiber and Frequency Shifting

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Solution Overview

Problem

Existing technologies face challenges in addressing bi-directional communication in a limited number of optical fiber link environments, particularly in mobile access networks, where back-reflection in optical fibers and connectors degrades transmission performance, and using separate optical fibers for each direction increases costs.

Innovation Solution

Implementing a bi-directional optical transmission method using a single optical fiber link with frequency shifting of optical signals by ±Δf, allowing the same wavelength to be used in both directions, reducing the influence of back-reflection and enabling bi-directional communication in a coherent optical communication system.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If separate optical fiber links are used for bidirectional transmission, then transmission performance is maintained, but device complexity and cost increase

Engineering Contradiction:

Improvetransmission performanceVSAvoidoptical fiber link configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines bidirectional optical transmission into a single optical fiber link by using frequency shifting to separate uplink and downlink signals. Instead of requiring separate fiber links for each direction, the system merges both directions into one fiber using different frequency bands, thereby reducing device complexity while maintaining transmission performance.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent introduces frequency as an additional dimension for signal separation. By shifting the frequency of optical signals by ±Δf, the system can distinguish between uplink and downlink transmissions on the same fiber, effectively adding a frequency dimension to resolve the spatial conflict of bidirectional transmission.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Device complexity

If the same wavelength is used for bidirectional transmission, then device complexity is reduced, but transmission performance deteriorates due to back-reflection

Engineering Contradiction:

Improveoptical transceiver configurationVSAvoidtransmission performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent changes the frequency parameter of the optical signals by applying ±Δf frequency shifting. This parameter change allows the system to use the same wavelength for bidirectional transmission while distinguishing between uplink and downlink signals through their different frequency offsets, thereby preventing back-reflection interference.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces frequency shifting as an intermediary mechanism between the transmitter and receiver. By applying frequency offsets to the optical signals, the system creates a clear distinction between transmitted and received signals, preventing the receiver from being overwhelmed by back-reflected signals at the same frequency.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If multiple laser light sources are used for bidirectional transmission, then transmission performance is maintained, but manufacturing cost increases

Engineering Contradiction:

Improvetransmission performanceVSAvoidoptical transceiver cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent makes a single laser light source perform multiple functions by using it for both uplink and downlink transmissions through frequency shifting. The same laser can generate signals for both directions, and the frequency-shifted versions allow the system to distinguish between transmitted and received signals, eliminating the need for separate laser sources for each direction.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 method maintains transmission performance by reducing the impact of back-reflection and lowers the cost of optical transceivers by using a single laser light source, thus optimizing fiber usage and reducing costs.

Implementation Method 1

frequency shifting of optical signals by ±Δf

Methodology Applied

Scientific EffectFrequency shifting:

Data Source

PatentUS20260031909A1Apparatus and method for transmitting and receiving optical signal in coherent optical communication system

Publication Date: 2026.01.29 ELECTRONICS & TELECOMM RES INST

AI summary

The present disclosure enables bi-directional optical transmission in a single optical fiber link using the same wavelength, thereby preventing transmission performance from being reduced due to the influence of back-reflection in an optical fiber, an optical connector, an optical element, or the like. An embodiment of the present disclosure is a method for transmitting and receiving an optical signal in a coherent optical communication system, including: transmitting, from a first transceiver, a first optical signal set to a first wavelength to a second transceiver; and receiving, from the second transceiver, a second optical signal set to the first wavelength.