Coherent Optical Receiver With Polarization Control for Low-Complexity Sensing
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Solution Overview
Problem
Coherent optical transmission technologies used in metro and core network segments are not suitable for 5G mobile technology and FTTH due to high complexity, cost, and power consumption, and they suffer from noise and low signal strength in network access segments.
Innovation Solution
A cost-effective coherent optical receiver design using a polarization-diversity actuator and a 2x2 coupler with photodiodes, controlled by electronic circuitry to modify ellipticity parameters, eliminating the need for complex DSP and OPLL, and enhancing optical receiver sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex DSP and OPLL arrangements are used to compensate polarization changes, then transmission continuity is ensured, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent extracts and eliminates the complex DSP and OPLL arrangements from the coherent optical receiver, retaining only the essential polarization diversity actuator and 2x2 coupler structure. This extraction resolves the contradiction by removing unnecessary complexity while preserving the core functionality needed for transmission continuity.
Solution Approach 2:
The patent replaces expensive, complex polarization tracking systems with a simpler, more cost-effective configuration using a polarization diversity actuator and 2x2 coupler. This substitution achieves acceptable transmission continuity at significantly lower device complexity and manufacturing cost.
2Productivity
If coherent optical transmission is used to achieve high data rates, then nominal data rates increase, but receiver sensitivity decreases due to low signal strength in access segments
Solution Approach 1:
The patent employs dynamic polarization control through the polarization diversity actuator, which continuously adapts to changing polarization states of the received signal. This dynamic adjustment maintains optimal signal strength and receiver sensitivity while supporting high data rate transmission in access network segments.
Solution Approach 2:
The patent changes the polarization state parameters of the local oscillator signal using the polarization diversity actuator to match the received signal's polarization state. This parameter adjustment optimizes the interference term in the photodetector output, thereby improving receiver sensitivity while maintaining high data rate capability.
3Reliability
If polarization diversity receivers with full diversity are used, then signal fading is avoided, but manufacturing cost and deployment complexity increase
Solution Approach 1:
The patent implements a partial polarization diversity approach using a simplified 2x2 coupler configuration with two photodiodes, rather than full polarization diversity receivers. This partial implementation is sufficient to avoid signal fading while significantly reducing manufacturing cost and deployment complexity for access network applications.
Solution Approach 2:
The patent replaces expensive full polarization diversity receivers with a cost-effective configuration using standard 2x2 couplers and photodiodes. This substitution achieves acceptable signal fading avoidance at much lower manufacturing cost, making it suitable for widespread deployment in access networks.
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
The design achieves low complexity, low cost, and high sensitivity, suitable for network access segments, improving data rates and split ratios in PON systems.
Implementation Method 1
a 2 x 2 coupler, having one input aiming at receiving the amplitude-shift keying modulated optical signal received from the coherent optical transmitter and the other input receiving another optical signal which is output by a set formed by a local oscillator and the polarization diversity actuator, so as to enable the local oscillator to provide a boosting effect to the amplitude-shift keying modulated optical signal
Implementation Method 2
two photodiodes, one photodiode of said photodiodes being connected to one output of the 2 x 2 coupler and the other photodiode of said photodiodes being connected to the other output of the 2 x 2 coupler. The coherent optical receiver is arranged to combine contributions from both photodiodes
Implementation Method 3
a polarization-diversity actuator configured for modifying an optical signal output by the local oscillator, so as to form an optical signal with elliptical polarization with main axis orientation φ l and ellipticity phase shift ψ l
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
A coherent optical receiver for amplitude-shift keying modulation comprises a local oscillator, a polarization-diversity actuator configured for modifying an optical signal output by the local oscillator and a 2 x 2 coupler for coupling the optical signal output by the polarization-diversity actuator and an amplitude-shift keying modulated optical signal from a coherent optical transmitter. The local oscillator thus provides a boosting effect to the amplitude-shift keying modulated optical signal. Two photodiodes are respectively connected to the outputs of the 2 x 2 coupler. The coherent optical receiver is arranged to combine contributions from both photodiodes in an additive manner and to generate an electrical signal representing the combined contributions. When the controlling unit detects that level of the electrical signal is insufficient, it instructs the polarization-diversity actuator to perform a modification of ellipticity main axis orientation and/ or a modification of ellipticity phase shift. Thus, low complex coherent optical receiver is achieved.