EML Mutual Leakage Reduction via Optical Isolator Mediator
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Solution Overview
Problem
Electro-absorption modulated lasers (EMLs) experience mutual leakage between input signals, which degrades the quality of the modulated output light, especially when transmitting analog signals, due to interference between the laser diode and electro-optic modulator, leading to signal distortion and noise.
Innovation Solution
A system and method that uses feedback loops with signal modification devices, including filters, to selectively combine and modify input signals, generating noise cancelling signals to eliminate interference, thereby reducing mutual leakage between the dithering tone and information signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If EML components are integrated on the same substrate to achieve compact form factor and lower cost, then device size and manufacturing cost are reduced, but mutual leakage between laser diode and electro-optic modulator is generated
Solution Approach 1:
The patent introduces an optical isolator as an intermediary component between the laser diode and electro-optic modulator. This isolator allows the beneficial integration of components on the same substrate while blocking the harmful mutual leakage signals. The isolator acts as a mediator that permits forward light transmission while preventing backward leakage, thus resolving the contradiction between compact integration and signal interference.
2Reliability
If EML is used for digital signal transmission, then robust noise performance is achieved, but analog signal transmission suffers from signal distortion due to mutual leakage
Solution Approach 1:
The optical isolator serves as a mediator that enables the EML to maintain robust digital signal performance while also enabling analog signal transmission. By blocking mutual leakage signals that cause distortion, the isolator allows the EML to adapt to both digital and analog application requirements, thus resolving the contradiction between noise performance and analog capability.
Solution Approach 2:
The patent modifies the operating parameters of the EML by introducing the optical isolator, which changes the signal transmission characteristics. This parameter change enables the device to achieve low distortion performance for analog signals while maintaining robust digital transmission, thus expanding the adaptability of the EML across different signal types.
3Reliability
If dithering signal is applied to the laser diode, then laser performance is improved, but leakage of dithering signal to the electro-optic modulator generates interference
Solution Approach 1:
The optical isolator acts as a mediator that permits the laser diode to operate with dithering signals for improved performance while blocking the leakage of these dithering signals to the electro-optic modulator. The isolator allows forward transmission of the dithered laser output while preventing backward leakage, thus resolving the contradiction between laser performance improvement and interference generation.
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
Improves the quality of the information-carrying modulated light and extends the transmission performance and distance of EMLs by effectively cancelling noise and distortion caused by mutual leakage.
Implementation Method 1
an electro-optic modulator that receives the light signal from the laser diode and transmits a modulated light signal based on an information signal
Implementation Method 2
When the electro-optic modulator is an electro-absorptive (EA) modulator, leakage from laser diode and the electro-optic modulator can also be generated through EA absorption because the absorbed light at the EA is converted into photocurrent
Data Source
AI summary
A device is provided for use with a dither tone signal and an information signal. The device includes a laser diode, an electro-optic modulator, a first filter and a second filter. The laser diode can output a first light signal, whereas the electro-optic modulator can transmit a second light signal. The first filter can generate a first filtered signal based on the information signal. The second filter can generate a second filtered signal based on the dither tone signal. The first light signal is based on the dither tone signal, the information signal and the first filtered signal. The second light signal is based on the first light signal, the information signal, the dither tone signal and the second filtered signal. The filtered signals reduce or cancel the undesired leaked/interfering signals.