WDM Coupler Branching Ratio for Raman Excitation Loss
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Solution Overview
Problem
In bus type optical access networks, the transmission distance is limited due to significant reduction in excitation light intensity as optical signals pass through multiple drop points, making it difficult to increase the maximum transmission distance effectively.
Innovation Solution
An optical communication system with a station-side apparatus and subscriber-side apparatuses in a bus network topology, featuring an optical amplification unit that amplifies downlink signals and outputs excitation light to amplify uplink signals, with a WDM optical coupler that adjusts the branching ratio based on the wavelength to minimize transmission loss of excitation light, and a mirror unit for intensity monitoring to determine the optimal excitation light wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If optical signals pass through multiple drop points in a bus type optical access network, then more subscribers can be served, but the excitation light intensity is significantly reduced
Solution Approach 1:
The patent changes the wavelength parameter of the excitation light to be different from the optical signal wavelength. By setting the excitation light wavelength outside the signal transmission bands (using wavelength division multiplexing), the excitation light experiences different transmission characteristics and can maintain higher intensity even after passing through multiple drop points, thus resolving the contradiction between serving more subscribers and maintaining excitation light intensity
Solution Approach 2:
The optical amplifier is designed to handle multiple wavelength channels simultaneously - it can amplify both the excitation light and the optical signals (downlink and uplink) through its gain medium. This multi-functionality allows the system to serve multiple subscribers while maintaining the excitation light intensity needed for Raman amplification of uplink signals
2Length of stationary object
If the transmission distance is increased in bus type optical access networks, then more distant subscribers can be connected, but the excitation light intensity reduces significantly
Solution Approach 1:
By changing the wavelength parameter of the excitation light to be distinct from signal wavelengths and positioning it in a spectral region with favorable transmission characteristics, the excitation light can traverse longer distances through the optical fiber with reduced attenuation, enabling extended transmission distance while maintaining sufficient intensity for Raman amplification
Solution Approach 2:
The excitation light is injected into the optical fiber in advance (from the OLT side) to establish a distributed Raman gain medium along the entire transmission path before the uplink signals are transmitted. This preliminary establishment of the amplification medium ensures that uplink signals are amplified along their propagation path, enabling longer 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 maintains high excitation light intensity over longer distances, maximizing Raman gain and thereby increasing the transmission distance in bus type optical access networks.
Implementation Method 1
an optical amplification unit that amplifies the downlink signal
Implementation Method 2
an excitation light output unit that outputs excitation light for amplifying an uplink signal to a communication path
Data Source
AI summary
An optical communication system configured with a station-side apparatus and a plurality of subscriber-side apparatuses in a bus network topology includes an optical amplification unit installed on a station side, and a drop unit configured to branch an optical signal and excitation light, wherein the optical amplification unit includes an amplifier configured to amplify a downlink signal, and an excitation light output unit configured to output the excitation light for amplifying an uplink signal to a communication path, and the drop unit changes a branching ratio in accordance with a wavelength of the optical signal so that a transmission loss of the excitation light with respect to a trunk fiber is reduced.