All-Optical Up-Conversion Using Dual Pump Four-Wave Mixing

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Solution Overview

Problem

Existing all-optical up-conversion techniques for radio-over-fiber systems are polarization sensitive, leading to conversion loss and sensitivity issues, which hinder seamless integration of wavelength-division multiplexed optical transport systems with ROF access networks.

Innovation Solution

An optical system utilizing dual co-polarized pump lightwaves generated through optical carrier suppression modulation, combined with a nonlinear medium for four-wave mixing, and an optical filter to produce phase-locked dual sideband signals without optical carriers, ensuring polarization insensitivity and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional all-optical up-conversion methods using external intensity or phase modulators with cross-absorption modulation in electro-absorption modulators are used, then up-conversion can be achieved, but conversion loss and sensitivity to polarization of optical signals occur

Engineering Contradiction:

Improvepolarization sensitivityVSAvoidconversion loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the fundamental parameter of the up-conversion mechanism from polarization-dependent cross-absorption modulation to polarization-independent four-wave mixing in nonlinear optical fiber. This parameter change eliminates sensitivity to input polarization state while achieving efficient up-conversion without the conversion losses associated with traditional modulator-based approaches

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/electrical modulation system (external intensity or phase modulators driven by RF signals) with a purely optical nonlinear process (four-wave mixing in optical fiber). This substitution eliminates the need for electrical-to-optical conversion and associated losses, achieving direct all-optical up-conversion with improved efficiency and polarization insensitivity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If single pump four-wave mixing is used for all-optical up-conversion, then broadband FWM effect can be achieved, but the scheme remains polarization sensitive

Engineering Contradiction:

Improvebroadband capabilityVSAvoidpolarization sensitivity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent segments the single pump source into two separate pump sources with different wavelengths. This segmentation enables the generation of multiple four-wave mixing products including the desired up-converted signal while eliminating polarization sensitivity through the combined effect of the two pump waves

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses a composite approach by combining two different wavelength pump sources to create a polarization-insensitive up-conversion system. The composite pumping scheme leverages the different polarization responses at different wavelengths to achieve overall polarization insensitivity while maintaining broadband capability

Inventive Principle:

Principle #40Composite materials

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 achieves polarization-insensitive and stable all-optical up-conversion, enabling efficient integration of WDM signals with ROF systems by maintaining consistent polarization direction and phase locking, thereby reducing conversion loss and sensitivity to signal orientation.

Implementation Method 1

a nonlinear medium for four wave mixing the baseband signal and two pump lightwaves to generate the baseband signal and corresponding dual sideband signals

Methodology Applied

Scientific EffectFour-wave mixing:

Implementation Method 2

an intensity modulator for generating two pump lightwaves that are carrier suppressed in response to the intensity modulator receiving a laser light source and being driven by an RF signal, wherein the intensity modulator is DC biased at a null point

Methodology Applied

Scientific EffectOptical carrier suppression modulation:

Implementation Method 3

an optical filter for filtering the carrier signals and providing wavelength division multiplexed signals without optical carriers

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Data Source

PatentUS8380083B2All optical up-conversion system

Publication Date: 2013.02.19 NEC CORP

AI summary

An optical system for providing all-optical up-conversion of a baseband signal including an all-optical up-converter responsive to baseband signals to provide corresponding dual sideband signals about a suppressed optical carrier, said dual sideband signals each having the same polarization direction, being phase locked, having the same optical power and having a fixed frequency spacing; and an optical filter for filtering the carrier signals and providing wavelength division multiplexed signals without optical carriers. In a preferred embodiment, the all-optical up-converter includes an intensity modulator for generating two pump lightwaves that are carrier suppressed in response to the intensity modulator receiving a laser light source and being driven by an RF signal, wherein the intensity modulator is DC biased at a null point, an optical combiner for combining the baseband signal and the two pump lightwaves, a nonlinear medium for four wave mixing the baseband signal and two pump lightwaves to generate the baseband signal and corresponding dual sideband signals, and an optical interleaver for removing the baseband signal and two pump lightwaves to provide said sideband signals about the suppressed optical carrier.