Optical Ring Modulator Pre-Compensation With Electrical Filtering
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Solution Overview
Problem
Optical ring modulators suffer from signal distortion due to the memory effect, causing trailing edge distortion in the output signal, which cannot be fully compensated by receiver-side analog-to-digital converters and signal processing, leading to degraded signal quality.
Innovation Solution
The use of electrical filters, specifically Infinite Impulse Response (IIR) and Finite Impulse Response (FIR) filters, to pre-compensate the optical ring modulator signals by generating electrical signals with slowly varying components that are applied to the modulator, thereby reducing signal distortion at the transmitter side.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If optical ring modulators are used for compact photonic integrated circuits, then device footprint is reduced, but signal distortion occurs due to memory effect
Solution Approach 1:
The patent applies preliminary action by pre-compensating the modulation signal before it is applied to the optical ring modulator. An equalizer circuit processes the input signal in advance to counteract the anticipated memory effect distortion, ensuring that the distorted signal from the ring modulator is corrected and produces a clean output signal without trailing edge distortion.
2Manufacturing precision
If receiver-side compensation is used to correct signal distortion, then signal quality can be improved, but noise is heavily increased and compensation range is limited
Solution Approach 1:
The patent implements preliminary action by moving the compensation function from the receiver side to the transmitter side. The equalizer circuit pre-processes the signal before optical modulation, eliminating distortion at its source rather than attempting to correct it after reception. This approach avoids amplifying noise that would occur with receiver-side digital signal processing and provides effective compensation for the full dynamic range of the modulator.
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 pre-compensates for signal distortion in the optical ring modulator output, improving signal quality by minimizing the reliance on receiver-side compensation and reducing noise, especially for signals with long tails.
Implementation Method 1
In these modulators, phase shift can be amplified by the cavity resonance effect without relying on long distance propagation
Implementation Method 2
the electrical input signal can be generated by an Infinite Impulse Response filter (IIR filter)
Implementation Method 3
or a Finite Impulse Response filter (FIR filter)
Data Source
AI summary
An optical ring circuit for modulating light from a light source into an optical signal includes a ring modulator located near a waveguide to couple a light propagating the waveguide, the ring modulator including a pair of electrodes, a signal generator to transmit an electrical signal corresponding to the optical signal, a filter circuit to generate an output signal, wherein the filter circuit includes an adder unit and at least one tap unit having a delay unit and a coefficient unit, wherein the adder unit adds the electrical signal from the signal generator and a signal passed from the tap unit for pre-compensating signal components of the electrical signal by at least twice delay time of the delay unit, and a driver circuit to apply a voltage to the electrodes based on the output signal.