Optical Source Orthogonal Polarization SMF Stability
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Solution Overview
Problem
In optical communications networks, especially in base station interconnections, the use of single mode fibre (SMF) for long distances leads to polarization state fluctuations due to temperature and external forces, causing intensity variations and performance issues with single-polarization devices, while the use of polarization maintaining fibre (PMF) is costly and attenuates signal strength.
Innovation Solution
An optical source comprising a laser, optical power splitter, phase changing equipment, polarization state setting equipment, and a polarisation beam coupler generates a composite optical signal with orthogonal polarization states, maintaining optical power within a preselected range over SMF, and includes mechanisms to compensate for frequency drift and phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If single mode fibre (SMF) is used for long distance transmission, then transmission distance is improved, but polarization state fluctuations occur causing intensity variations and performance issues
Solution Approach 1:
The invention segments the optical signal into two separate polarization components (first and second optical signals with orthogonal polarization states). Each component is transmitted independently through the SMF, and their powers are adjusted so that their sum maintains a stable total optical power at the receiver, compensating for polarization fluctuations during transmission.
Solution Approach 2:
The invention changes the parameter of optical power distribution between two orthogonal polarization states. By independently controlling and adjusting the power levels of the first and second optical signals, the system adapts to polarization fluctuations in the SMF, ensuring that the combined optical power remains stable despite environmental variations.
2Reliability
If polarization maintaining fibre (PMF) is used to maintain polarization state, then signal stability is improved, but cost and attenuation increase significantly
Solution Approach 1:
The invention replaces expensive PMF with inexpensive SMF by using a different approach - transmitting multiple polarization components with adjusted power levels. This uses a cheaper optical medium (SMF) while achieving the same goal of stable signal transmission through power balancing of orthogonal polarization components.
3Reliability
If polarization maintaining fibre (PMF) is used to maintain polarization state, then signal stability is improved, but signal attenuation increases
Solution Approach 1:
The invention replaces high-loss PMF with low-loss SMF by transmitting multiple polarization components. The power adjustment mechanism ensures that the combined signal maintains stability while utilizing the lower attenuation characteristics of standard single mode fibre.
4Adaptability or versatility
If depolarised broadband light source is used to provide arbitrary polarization states, then polarization flexibility is improved, but transmission distance is limited due to chromatic dispersion and low power
Solution Approach 1:
The invention uses a narrow-linewidth laser that provides coherent light with stable polarization properties, combined with periodic power adjustment of the orthogonal components. This approach maintains transmission distance by using coherent light while achieving polarization flexibility through power balancing of the two orthogonal components.
Solution Approach 2:
The invention creates a composite optical signal by combining two coherent light components with orthogonal polarization states. This composite signal maintains the advantages of coherent light (long transmission distance) while achieving polarization flexibility through the superposition of orthogonal components with adjustable power levels.
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 allows for stable transmission of optical signals with arbitrary polarization states over tens of kilometers of SMF, ensuring good performance of single-polarization photonic devices and reducing phase noise, making it suitable for high-speed optical communications.
Implementation Method 1
a laser configured to generate an optical signal
Implementation Method 2
a first optical power splitter configured to split the optical signal into a first optical signal and a second optical signal
Implementation Method 3
phase changing equipment configured to change a phase of at least one of the first optical signal and the second optical signal
Implementation Method 4
polarisation state setting equipment configured to set a polarisation state of at least one of the first optical signal and the second optical signal such that the first optical signal has a first state of polarisation and the second optical signal has a second state of polarisation substantially orthogonal from the first state of polarisation
Implementation Method 5
a polarisation beam coupler configured to combine the first optical signal and the second optical signal into a composite optical signal
Data Source
AI summary
The present invention provides an optical source comprising a laser, a first optical power splitter, phase changing equipment, polarisation state setting equipment, a polarisation beam coupler and an output. The laser is configured to generate an optical signal. The first optical power splitter is configured to split the optical signal into a first optical signal and a second optical signal. The phase changing equipment is configured to change the phase of at least one of the first optical signal and the second optical signal such that the first optical signal has a first phase and the second optical signal has a second phase different from the first phase by a preselected phase difference. The polarisation state setting equipment is configured to set the polarisation state of at least one of the first optical signal and the second optical signal such that the first optical signal has a first state of polarisation and the second optical signal has a second state of polarisation substantially orthogonal from the first state of polarisation. The polarisation beam coupler is configured to combine the first optical signal and the second optical signal into a composite optical signal comprising both the first optical signal and the second optical signal having said orthogonal states of polarisation. The output is arranged to output at least a portion of the composite optical signal.