Double-Pass Optical Fibre Amplifier Layout for Reflection Loss Control
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Solution Overview
Problem
Double-pass optical fibre amplifiers (DPOAs) incorporating acousto-optic modulators (AOMs) suffer from reflection losses that lead to signal distortion, overmodulations, and increased complexity in architecture, requiring additional components and reduced gain in doped optical fibre amplifiers.
Innovation Solution
The proposed optical device includes an AOM, a laser, upstream and downstream polarization-maintaining optical fibres, and a reflection means. The downstream fibre is arranged to have a non-zero transit time for the optical beam, and the AOM's input/output faces form a non-zero angle, reducing parasitic reflections and improving signal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an AOM is integrated into a double-pass optical fibre amplifier, then the amplifier can modulate the optical signal, but reflection losses from the AOM cause signal distortion and overmodulations
Solution Approach 1:
The patent introduces a circulator as an intermediary component between the AOM and the optical fibre amplifier. The circulator directs the optical signal through the AOM in a controlled manner, allowing the AOM to modulate the signal while preventing reflected light from re-entering the amplifier and causing overmodulations. This mediator component enables both modulation functionality and signal stability.
2Reliability
If additional components are added to counter reflection losses, then signal stability improves, but device complexity increases
Solution Approach 1:
The circulator performs multiple functions within a single component: it directs the optical signal through the AOM, isolates the amplifier from reflected light, and enables the double-pass configuration. This multi-functional approach achieves signal stability without requiring multiple separate components, thereby reducing overall device complexity while maintaining reliability.
3Reliability
If the gain of the EDFA is reduced to prevent overmodulations, then signal stability improves, but amplification performance deteriorates
Solution Approach 1:
The circulator acts as a mediator that prevents reflected light from reaching the EDFA, thereby eliminating the source of overmodulations. This allows the EDFA to operate at its full gain capability without causing signal instability, thus maintaining both high amplification performance and signal stability simultaneously.
4Reliability
If reflection losses are attenuated, then signal quality improves, but additional components and architectural changes are required
Solution Approach 1:
The circulator serves as an intermediary component that naturally attenuates reflection losses by directing reflected light away from the optical path. This single-component solution improves signal quality without requiring multiple additional components or complex architectural modifications, thereby achieving high signal quality with minimal increase in device complexity.
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 attenuates overmodulations and reduces reflection losses, enhancing the performance of DPOAs by stabilizing the temporal shape of signals and simplifying the architecture, while maintaining high-speed, high-power, and small spectral width pulsed optical signals.
Implementation Method 1
an acousto-optic modulator (AOM)
Implementation Method 2
the upstream fibre is a polarization-maintaining optical fibre capable of maintaining a linear polarization state of an optical beam
Implementation Method 3
a reflection means connected to the downstream fibre of the AOM and arranged to reflect a beam originating from the downstream fibre into the downstream fibre
Implementation Method 4
a doped optical fibre amplifier (EDFA type)
Data Source
AI summary
An optical device including an acousto-optic modulator (AOM), a laser, an upstream optical fibre extending between the laser and the AOM, a downstream optical fibre located downstream of the AOM and a reflector connected to the fibre downstream of the AOM. The optical device including the upstream fibre is a polarisation-maintaining optical fibre, and/or the downstream fibre is arranged so that a transit time of the optical beam through said downstream fibre from the AOM to the reflecting means is nonzero and shorter than or equal to half an open duration of the AOM, and/or the AOM includes a crystal in which the entrance/exit faces are planar and are at a nonzero angle to each other, and/or at least one of the two entrance/exit faces is at a nonzero angle to a direction of propagation of the acoustic wave in the crystal.