Front-Exciting Raman Amplifier Gain Control Without Signal Interruption
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Solution Overview
Problem
The challenge in WDM transmission systems is setting the Raman gain of front-exciting Raman amplifiers without disrupting ongoing operations, as the relative intensity noise from the excitation light source interferes with measuring amplified spontaneous scattered light, making it difficult to determine the gain when an optical signal is communicated.
Innovation Solution
A controller that acquires communication-related information to set the Raman gain based on either the light intensity of amplified spontaneous scattered light when the signal is not communicated or the optical signal intensity when it is, allowing for gain adjustment regardless of signal presence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Raman gain is set based on amplified spontaneous scattered light intensity, then the gain setting is simple and direct, but the measurement is interfered with by relative intensity noise from the excitation light source when optical signal is communicated
Solution Approach 1:
The controller determines the communication state of the optical signal before proceeding with gain setting. When no communication is detected, the controller then measures the amplified spontaneous scattered light intensity to set the Raman gain, avoiding measurement interference during active communication
Solution Approach 2:
The gain setting methodology dynamically changes based on the communication state. The system switches between two different gain setting approaches: using amplified spontaneous scattered light measurement when idle, and using optical signal intensity measurement when communication is active, optimizing performance for each state
2Measurement precision
If the WDM transmission system is stopped to set the Raman gain, then the gain can be accurately determined without signal interference, but the operational efficiency deteriorates
Solution Approach 1:
The system dynamically adapts the gain setting method based on whether optical signals are present. During active communication, the controller uses optical signal intensity to determine Raman gain without stopping transmission. When idle, it uses amplified spontaneous scattered light measurement. This eliminates the need to stop the system while maintaining accurate gain setting
Solution Approach 2:
The controller changes the measurement parameter based on communication state: using amplified spontaneous scattered light intensity when no signal is present, and switching to optical signal intensity when communication is active. This parameter adaptation enables continuous operation without compromising measurement accuracy
3Device complexity
If a single gain setting method is used for both communication and non-communication states, then the control system is simple, but the gain setting accuracy deteriorates when optical signal is present
Solution Approach 1:
The control system dynamically selects the appropriate gain setting method based on the communication state detected by the controller. When optical signals are absent, it uses amplified spontaneous scattered light measurement. When signals are present, it switches to optical signal intensity measurement, maintaining accuracy across different operational states
Solution Approach 2:
The system changes the measurement parameter according to communication state: using amplified spontaneous scattered light intensity for idle state gain setting, and optical signal intensity for active communication state gain setting. This parameter adaptation maintains measurement precision without requiring overly complex control logic
Data Source
AI summary
A controller for a front-exciting Raman-amplifier that amplifies an optical signal transmitted from one end of an optical fiber to other end by inputting an excitation light to the one end, the controller includes a memory, and a processor coupled to the memory and configured to acquire communication-related information regarding communication of the optical signal in the optical fiber, when the acquired communication-related information does not indicate the communication of the optical signal, set a Raman gain of the front-exciting Raman amplifier based on a first light intensity of an amplified spontaneous scattered light of the excitation light, and when the acquired communication-related information indicates the communication of the optical signal, set the Raman gain based on a second light intensity of the optical signal output from the optical fiber.