Distributed Raman Amplifier Gain Control via Reference Light
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Solution Overview
Problem
Conventional distributed Raman amplifiers face challenges in achieving precise automatic gain control, leading to degradation of transmission characteristics due to changes in fiber characteristics and types, as existing methods using reference lights with separate wavelengths result in significant errors in compensating gain wavelength characteristics.
Innovation Solution
A distributed Raman amplifier configuration that includes a reference light source with a wavelength within the gain band of the Raman amplification, multiplexed with the WDM signal light, and a control section that maintains a constant ratio of Raman gains between the WDM signal light and the reference light, allowing for precise automatic gain control and compensation of gain wavelength characteristics using a fixed gain equalizer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed gain equalizer is used to compensate gain wavelength characteristics, then the device complexity is reduced, but the manufacturing precision of gain compensation deteriorates due to changes in gain wavelength characteristics with operating state
Solution Approach 1:
The patent implements automatic gain control that dynamically adjusts the pumping light power based on monitored signal light power to maintain constant average gain. This dynamic adjustment compensates for changes in gain wavelength characteristics caused by fiber deterioration or type changes, allowing the fixed gain equalizer to maintain effective compensation without requiring complex adaptive structures.
Solution Approach 2:
The patent employs a feedback mechanism where the signal light power is monitored and used to control the pumping light power. This feedback loop ensures that the average gain remains constant, preventing degradation of transmission characteristics and maintaining the effectiveness of the fixed gain equalizer across varying operating conditions.
2Ease of operation
If the pumping light power is controlled at constant to realize automatic gain control, then the ease of operation is improved, but the reliability of transmission characteristics deteriorates when fiber characteristics change
Solution Approach 1:
The patent uses a feedback mechanism where the signal light power is monitored and used to adjust the pumping light power. This ensures that the average gain remains constant even when fiber characteristics change due to deterioration or type variations, maintaining reliable transmission characteristics while keeping the control mechanism simple.
Solution Approach 2:
The system automatically adjusts the pumping light power based on monitored signal light power without requiring external intervention. This self-adjusting mechanism maintains constant average gain and reliable transmission characteristics while simplifying operation.
3Measurement precision
If reference light with separate wavelength is used for gain control, then the measurement precision of gain is improved, but the manufacturing precision of gain wavelength characteristics compensation deteriorates due to significant errors
Solution Approach 1:
The patent uses a reference light with wavelength within the gain band that copies the Raman amplification characteristics experienced by the signal light. This reference light undergoes the same Raman gain process, allowing accurate measurement and control of the actual gain wavelength characteristics without the errors introduced by using significantly different wavelengths.
Solution Approach 2:
The patent changes the parameter of reference light wavelength to be within the gain band rather than separate from it. This parameter change allows the reference light to experience similar Raman amplification conditions as the signal light, enabling precise control of gain wavelength characteristics while maintaining measurement precision.
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 enables precise control of the average gain of the distributed Raman amplification, reducing compensation errors in wavelength characteristics and achieving excellent transmission characteristics across different fiber types and conditions.
Implementation Method 1
a pumping light source that generates a pumping light for distributed Raman amplifying a WDM signal light propagated through an optical transmission path
Implementation Method 2
a reference light source that generates a reference light having a wavelength set within a gain band of the distributed Raman amplification
Implementation Method 3
a multiplexer that multiplexes the reference light output from the reference light source with a WDM signal light to supply the multiplexed light to one end of the optical transmission path
Implementation Method 4
a control section that controls the pumping light source on the basis of a monitor result in a monitor section, so that a ratio of Raman gains in the WDM signal light and the reference light is maintained at constant
Data Source
AI summary
In a distributed Raman amplifier according to the present invention, a WDM signal light and a reference light are supplied to one end of an optical transmission path to which a pumping light is supplied; the WDM signal light and the reference light, which are propagated through the optical transmission path, are subjected to the distributed Raman amplification; the powers of the WDM signal light and the reference light, which are output from the other end of the optical transmission path, are monitored; and pumping light sources are controlled based on the monitor result. A wavelength of the reference light is set within a gain band of the distributed Raman amplification but longer or shorter than a wavelength of the WDM signal light, and also, set to be in a wavelength region in which a fluctuation amount of a Raman gain in the wavelength of the reference light becomes equal to or smaller than ⅕ of a fluctuation amount of a Raman gain in the wavelength band of the WDM signal light. As a result, it is possible to realize a low-cost distributed Raman amplifier of a simple configuration, capable of realizing an automatic gain control with high precision and also capable of compensating for gain wavelength characteristics using a fixed gain equalizer.