Optical Transmitter Pump Laser Modulation for Auxiliary Signal Control
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Solution Overview
Problem
Existing optical transmitters using phase modulation schemes for monitoring control signals in optical fiber transmission systems face challenges with high insertion loss, requiring additional amplification stages like EDFA, and lack specific methods for controlling these signals effectively.
Innovation Solution
The method involves a wavelength tunable light source, optical modulator, EDFA, variable optical attenuator, and pump laser controller to maintain output power and modulate intensity for auxiliary signals, allowing for feedback control and suspension of phase modulation to transmit auxiliary signals with tunable wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase modulation scheme is used for monitoring control signals, then signal transmission is achieved, but insertion loss increases requiring additional optical amplifiers
Solution Approach 1:
The patent combines the monitoring control signal with the main communication signal by modulating the pump laser that excites the EDFA. This allows both signals to share the same optical path and amplifier, eliminating the need for separate amplification stages and reducing insertion loss while maintaining reliable signal transmission.
Solution Approach 2:
The pump laser serves dual functions: it provides excitation light for the EDFA to amplify the main signal, and simultaneously carries the monitoring control signal through intensity modulation. This multi-functionality reduces system complexity and eliminates additional signal paths that would increase insertion loss.
2Stability of the object's composition
If feedback control is maintained for pump laser and VOA, then output power stability is improved, but auxiliary signal transmission capability deteriorates
Solution Approach 1:
The system dynamically switches between two operational modes: during normal operation, feedback control maintains stable output power; when auxiliary signal transmission is needed, the feedback control is temporarily suspended to allow intensity modulation of the pump laser. This dynamic adaptation resolves the contradiction between stability and versatility.
Solution Approach 2:
The pump laser operates in periodic cycles, alternating between feedback-controlled stable operation for main signal transmission and intensity-modulated operation for auxiliary signal transmission. This periodic switching enables both functions to be performed effectively at different times.
3Adaptability or versatility
If pump laser intensity is modulated for auxiliary signals, then auxiliary signal transmission is enabled, but main signal output power control deteriorates
Solution Approach 1:
The system dynamically adjusts the pump laser operation mode based on transmission needs. During auxiliary signal transmission, intensity modulation is applied; during normal operation, feedback control restores precise power control. This dynamic switching resolves the contradiction between adaptability and power control.
Solution Approach 2:
The system preliminarily suspends feedback control before initiating auxiliary signal transmission to prevent interference with intensity modulation. After auxiliary signal transmission completes, feedback control is restored to re-establish precise power control, ensuring both functions operate optimally without mutual interference.
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 approach enables efficient power control and modulation of auxiliary signals, improving the monitoring and administration of optical fiber transmission systems by maintaining desired output power and allowing for the transmission of auxiliary signals with longer cycles than main signals.
Implementation Method 1
an erbium-doped optical fiber amplifier (EDFA) that amplifies the main signal by using the excitation light
Implementation Method 2
an optical modulator that outputs a main signal generated by phase modulation of the continuous wave light
Data Source
AI summary
A method of controlling an optical transmitter includes steps of amplifying, by an EDFA, a main signal output from an optical modulator, attenuating and outputting, by a VOA, the main signal amplified and output by the EDFA, and maintaining an output power of the main signal output from the VOA at a predetermined value, suspending the phase modulation in the optical modulator to output continuous wave light from the optical modulator, disabling feedback control of the VOA that is performed by the VOA controller and maintaining a constant control signal of the VOA, disabling feedback control of a pump laser that is performed by a pump laser controller, and controlling the pump laser to modulate an intensity of the excitation light and generate an auxiliary signal having a cycle longer than a cycle of the main signal.