Optical Receiver Gain Control Using Integrated VOA Attenuation

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Solution Overview

Problem

Existing optical receivers struggle to handle high-speed optical data applications with large dynamic range optical signals, requiring TIA's with large dynamic ranges which are difficult and costly to implement.

Innovation Solution

The integration of a Variable Optical Attenuator (VOA) within an electro-photonic integrated circuit, coupled with a photodiode and a transimpedance amplifier, allows for signal level adjustment in the optical domain. This setup adjusts the bias of the VOA based on the optical input signal level, limiting the photocurrent to a narrow range and reducing the dynamic range requirements of the TIA.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a TIA with large dynamic range is used to handle optical signals with large dynamic range, then the receiver can process signals with varying optical power levels, but the device complexity and cost increase significantly

Engineering Contradiction:

Improvedynamic range handling capabilityVSAvoidTIA complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent segments the dynamic range handling function between two components: the VOA handles the optical signal attenuation to reduce dynamic range, and the TIA handles the amplified electrical signal with a smaller, fixed dynamic range. This segmentation allows each component to be optimized for its specific function, reducing overall system complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The VOA acts as an intermediary component between the optical input and the photodiode-TIA system. It mediates the large dynamic range optical signals by attenuating them to a smaller dynamic range before detection, allowing the TIA to operate with simplified design parameters.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If a TIA with large dynamic range is implemented, then high-speed optical data applications can be supported, but the settling time increases

Engineering Contradiction:

Improveoptical data processing capabilityVSAvoidsettling time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The VOA performs preliminary action by attenuating the optical signal to the appropriate level before it reaches the photodiode and TIA. This pre-adjustment ensures that the TIA receives signals within its optimal dynamic range from the start, eliminating the need for the TIA to settle across a wide dynamic range and reducing overall settling time.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the mechanical/electrical dynamic range adjustment within the TIA with an optical domain adjustment using the VOA. This substitution allows the TIA to operate with fixed, optimized parameters while the VOA dynamically adjusts the optical signal level, resulting in faster response and reduced settling time.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If silicon electronics are used to set TIA input level, then burst-mode operation can be achieved, but the cost increases

Engineering Contradiction:

Improveburst-mode operation capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent substitutes silicon-based electronic dynamic range adjustment with a photonic solution using a VOA. The VOA can be monolithically integrated with InP-based photodiodes and TIAs, eliminating the need for separate silicon electronics and reducing manufacturing complexity and cost while maintaining burst-mode operation capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent merges the VOA with the InP-based photodiode and TIA into a monolithic integrated circuit. This integration combines multiple functions (optical attenuation, photodetection, and transimpedance amplification) into a single semiconductor platform, reducing the need for separate silicon electronics and lowering overall manufacturing cost.

Inventive Principle:

Principle #5Merging (Combining)

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 solution effectively mitigates the need for TIA's with large dynamic ranges, allowing for improved performance and reduced settling time while preserving and extending the dynamic range of optical signal input levels.

Implementation Method 1

a Variable Optical Attenuator (VOA)... providing an attenuated optical input signal to the photodiode

Methodology Applied

Scientific EffectOptical absorption: Absorption (EM radiation)

Implementation Method 2

a photodiode (PD)... providing a photocurrent output

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS20250070886A1Electro-photonic circuit comprising an optical receiver with optical gain control

Publication Date: 2025.02.27 ELECTROPHOTONIC IC INC

AI summary

An optical receiver comprises a variable optical attenuator (VOA), a photodiode (PD) which may be a pin-PD or an APD, a transimpedance amplifier (TIA), and a feedback/control circuit for adjusting a bias voltage of the VOA in response to an optical input signal level, to provide an attenuated optical output signal to the PD having a narrower dynamic range. Providing signal level adjustment in the optical domain mitigates the requirement for a TIA with a large dynamic range and provides for fast switching. The optical receiver may comprise a waveguide configuration, wherein a first electro-absorption modulator (EAM) is operable as the VOA and a second EAM is operable as the photodiode. A monolithically integrated electro-photonic circuit comprising the VOA, PD, TIA and feedback/control circuit may be provided using InP-based semiconductor materials.