Optical Modulator Wavelength Stabilization via BER Feedback
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Solution Overview
Problem
Silicon Photonic optical transmitters with optical ring resonator modulators face issues due to temperature-dependent changes in refractive index, which affect resonance and bit error rate (BER), and existing temperature compensation systems are limited by aging and other factors.
Innovation Solution
An optical transmitter system that includes an optical modulator with a heater controlled by a circuit computing bit errors in the received digital data stream, actively adjusting the resonance wavelength by applying heat based on detected errors to maintain optimal operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a temperature sensor and micro-heater are used to compensate for temperature-induced resonance shifts, then the resonance wavelength stability is improved, but the bit error rate deteriorates over time due to sensor aging
Solution Approach 1:
The patent implements feedback control by monitoring the actual bit error rate and adjusting the heater power accordingly. The controller receives BER measurements from the optical receiver and uses this feedback to dynamically adjust the heater current, optimizing the resonance wavelength to minimize bit errors. This closed-loop feedback mechanism replaces the open-loop temperature sensor approach, eliminating sensor aging issues while maintaining resonance stability.
Solution Approach 2:
The patent changes the control parameter from temperature sensing to bit error rate monitoring. Instead of using a temperature sensor to infer the needed heater adjustment, the system directly measures the performance impact (bit errors) and adjusts the heater to optimize this parameter. This parameter change bypasses the aging temperature sensor problem while achieving the same goal of resonance wavelength stabilization.
2Reliability
If the resonance wavelength is actively controlled to maintain optimal performance, then the bit error rate is improved, but the device complexity increases due to additional control circuitry
Solution Approach 1:
The patent makes the control circuit multi-functional by using the same controller for both temperature compensation and bit error rate optimization. The controller performs multiple functions: monitoring BER, calculating optimal heater power, and adjusting the heater current. This universal approach consolidates control functions into a single integrated circuit, reducing overall device complexity compared to having separate dedicated circuits for each function.
Solution Approach 2:
The system performs self-optimization by automatically monitoring its own performance (bit errors) and adjusting its own operating conditions (heater power) without external intervention. The controller continuously measures BER and autonomously adjusts the heater to minimize errors, enabling the system to self-correct and maintain optimal performance without requiring complex external control infrastructure.
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 effectively stabilizes the resonance wavelength, improving bit error rate by dynamically compensating for temperature-induced shifts, thereby enhancing the reliability of optical signal modulation and transmission.
Implementation Method 1
The index of refraction within the ring changes with operating temperature
Data Source
AI summary
The present invention relates to an optical transmitter that includes an optical modulator configured to modulate an optical signal with a digital data stream, and a heater configured to apply heat to the optical modulator. The optical transmitter also includes an optical receiver configured to receive the modulated optical signal and to convert the modulated optical signal into a received digital data stream. A circuit is configured to compute bit errors in the received digital data stream by comparing the received digital data stream with the digital data stream, and control the heater based on the computed bit errors.