Photonic Integrated Circuit Back Reflection Noise Suppression
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Solution Overview
Problem
Passive optical networks (PONs) face challenges in designing cost-effective transceivers for optical line terminals (OLTs) and optical network units (ONUs) that can efficiently manage bidirectional communication while minimizing the impact of back reflections and unwanted noise, particularly in high-bandwidth applications like fiber-to-the-home (FTTH) deployments.
Innovation Solution
A photonic integrated circuit (PIC) with a modulated transmitter laser diode and receiving photodetectors, incorporating a multimode interference coupler and a back facet monitoring photodetector/absorber to direct and absorb unwanted signals, ensuring minimal interference and improved absorption of both TE and TM polarization modes, along with distributed waveguides for mode adaptation between active and passive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a photonic integrated circuit includes both a transmitter laser diode and a receiving photodetector on the same chip, then bidirectional communication functionality is achieved, but back reflection noise from the laser diode interferes with the receiving photodetector
Solution Approach 1:
The patent extracts the harmful back reflection noise from the signal path by introducing a dedicated absorber component that captures the laser diode's back reflected light before it can reach the receiving photodetector. This separation of functions allows the laser and photodetector to coexist on the same chip while eliminating the interference problem.
Solution Approach 2:
The patent introduces an intermediary absorber component positioned between the laser diode and the receiving photodetector. This absorber acts as a mediator that intercepts and absorbs the harmful back reflection noise, preventing it from reaching the photodetector while allowing the useful signal to pass through unaffected.
2Adaptability or versatility
If a photonic integrated circuit integrates multiple active elements including laser diodes and photodetectors, then device functionality is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple active elements (laser diode, receiving photodetector, and absorber) into a single photonic integrated circuit chip. By combining these functions onto one substrate with integrated waveguides, the patent reduces the need for separate discrete components and their associated interconnections, thereby managing complexity while enhancing functionality.
Solution Approach 2:
The patent designs the integrated circuit to perform multiple functions: the laser diode transmits optical signals, the photodetector receives optical signals, and the absorber eliminates back reflection noise. This multi-functional design allows a single device to handle bidirectional communication and noise suppression, reducing the need for multiple separate devices.
3Object-affected harmful factors
If the absorbing element is positioned close to the laser diode, then back reflection noise is effectively absorbed, but the absorber may absorb useful signal light as well
Solution Approach 1:
The patent applies local quality by designing the absorber with specific optical properties tailored to its location. The absorber is positioned and configured to selectively absorb back reflection noise from the laser diode while being designed to be transparent to the useful signal light wavelengths, thereby eliminating noise without sacrificing signal transmission.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the absorber's optical characteristics, such as its material composition and physical dimensions, to match the wavelength of the back reflection noise while remaining transparent to the signal light. This precise parameter tuning allows selective absorption of harmful noise while preserving useful signals.
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 solution enhances the performance of PON transceivers by reducing back reflection noise, improving signal detection accuracy, and maintaining low production costs, thus addressing the need for efficient and cost-effective bidirectional communication in PONs.
Implementation Method 1
a multimode interference (MMI) coupler set to direct a substantial portion of the incoming communication signal to the receiving photodetector and to direct a substantial portion of the outgoing communication signal from the laser diode to the input/output port
Implementation Method 2
the active region of the power monitoring photodetector is made sensitive to absorption of polarized light of both the TE and TM polarization modes of this back reflected light that is unwanted noise propagating in and received from the passive optical network (PON)
Implementation Method 3
distributed waveguides for mode adaptation between active and passive elements
Data Source
AI summary
A photonic integrated circuit (PIC) for a PON transceiver comprises a single monolithic chip having a modulated transmitter laser diode of a first wavelength, λ1, for generating a first communication signal outgoing from the chip via an input/output port and a receiving photodetector for receiving a second communication signal of a second wavelength, λ2, onto chip incoming from the input/output port and a monitoring photodetector for receiving a portion of the first communication signal to monitor the laser diode output power.