Optical Receiver PIN APD Polarization Control
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Solution Overview
Problem
Conventional optical receivers using avalanche photodiodes (APDs) face challenges in controlling the avalanche multiplication factor due to temperature variations and polarization state effects, leading to inconsistent signal light incidence and difficulty in maintaining a constant multiplication factor.
Innovation Solution
The optical receiver incorporates a PIN photodiode and an avalanche photodiode, where the PIN photodiode receives signal light and transmits a portion to the avalanche photodiode, allowing for constant light incidence and using a control mechanism to adjust the supply voltage or current based on output current values to maintain a predetermined avalanche multiplication factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the APD receives signal light at an angle for multiplication factor control, then the multiplication factor can be controlled, but the reflectance varies depending on polarization state causing inconsistent light incidence
Solution Approach 1:
A beam splitter is introduced as an intermediary component between the optical fiber and the APD. The beam splitter divides the signal light into two paths: one path directs light to the APD for multiplication factor control, while the other path directs light to a reference photodiode. This intermediary device ensures that both paths receive light with consistent intensity regardless of polarization state, thereby maintaining reliable light incidence while enabling precise multiplication factor control.
2Power
If high reverse bias voltage is applied to the APD for avalanche multiplication, then signal amplification is achieved, but the operating characteristics become extremely sensitive to temperature variation
Solution Approach 1:
The patent implements a feedback control mechanism where a reference photodiode continuously monitors the intensity of signal light incident on the APD. The output from the reference photodiode is fed back to a control circuit that adjusts the reverse bias voltage applied to the APD. This feedback loop compensates for temperature-induced variations in avalanche multiplication factor, maintaining stable operating characteristics while preserving the high signal amplification capability provided by the avalanche effect.
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 enables effective control of the avalanche multiplication factor, independent of temperature variations and polarization states, ensuring consistent signal processing and improved performance in optical communication systems.
Implementation Method 1
the PIN photodiode has an incident surface for receiving signal light and transmits a part of the signal light to the surface opposite to the incident surface
Implementation Method 2
an avalanche photodiode (hereafter abbreviated as APD) as a photodetector... APDs have a function to amplify signal photocurrents... the APD is operated at a voltage close to a breakdown voltage of a PN junction
Data Source
AI summary
An optical receiver includes a PIN photodiode (PIN-PD) having an incident surface for receiving signal light, the PIN-PD transmitting a part of the signal light to the surface opposite to the incident surface, and an avalanche photodiode (APD) having an incident surface for receiving light transmitted through the PIN-PD. In the optical receiver, the ratio of the quantity of signal light detected by the PIN-PD and the ratio of the quantity of signal light detected by the APD are not affected by the polarization state of the signal light incident on the optical receiver, and accordingly the avalanche multiplication factor of the APD is suitably controlled on the basis of the signal light detected by the PIN-PD.