Optical Domain Despreading for High-Bandwidth CDMA
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Solution Overview
Problem
Conventional CDMA despreading in optical fiber access networks is limited by electrical rate constraints, making it difficult to meet the bandwidth requirements for high-speed services like video on demand and high-definition television.
Innovation Solution
The method involves transferring the despreading operation from the electrical domain to the optical domain, using optical splitters, modulators, and couplers to perform field modulation and phase deflection on optical signals, allowing for higher chip rates and increased bandwidth, with accumulation occurring only in the electrical domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If CDMA despreading is performed in the electrical domain, then the system is easier to implement with conventional electronics, but the data rate is limited by electronic rate constraints and cannot meet high-speed service requirements
Solution Approach 1:
The patent replaces the electrical domain despreading system with an optical domain system. Specifically, it uses optical modulators to perform code multiplication and optical accumulators to perform integration, substituting electronic components with optical components that operate at much higher frequencies, thereby achieving both ease of implementation through standardized optical components and high data rates exceeding 100 Gbps
Solution Approach 2:
The patent changes the operating domain from electrical to optical, utilizing the fundamentally different parameters of optical signals (higher frequency, larger bandwidth) compared to electrical signals. This parameter change enables the system to achieve data rates of 100 Gbps and above while maintaining the despreading functionality through optical field modulation and detection
2Device complexity
If conventional electrical domain despreading is used, then the device complexity is lower with standard electronic components, but the bandwidth capacity is insufficient for future high-speed image services
Solution Approach 1:
The patent substitutes electrical domain components with optical domain components. The optical modulator replaces electronic mixers, optical accumulators replace electronic integrators, and photodetectors replace electronic converters. This substitution maintains relatively simple device architecture while achieving bandwidth capacities of 100 Gbps and above, sufficient for high-speed image services like HDTV and VOD
Solution Approach 2:
The optical despreading apparatus can serve multiple functions: it performs despreading for CDMA signals, supports multiple users simultaneously, and can be integrated into existing optical access networks. The same optical components can handle different data rates and service types, providing universal functionality that meets both current and future bandwidth requirements
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 approach enables higher chip rates up to 20 GHz or 25 GHz, supporting maximum rates of 100 Gbps per wavelength, effectively meeting user bandwidth demands while reducing costs compared to traditional methods.
Implementation Method 1
an optical modulator configured to perform field modulation on the second optical signal
Implementation Method 2
the optical coupler configured to perform phase deflection processing on the first optical signal and the third optical signal
Implementation Method 3
a balanced receiver configured to superimpose the fourth optical signal and the fifth optical signal to generate a first electrical signal
Data Source
AI summary
An apparatus for despreading in an optical domain configured to split a received optical signal into a first optical signal and a second optical signal, perform phase deflection on the second optical signal, output a third optical signal, perform phase deflection on the first optical signal and the third optical signal, output a fourth optical signal and a fifth optical signal to a balanced receiver, and superimpose the fourth optical signal and the fifth optical signal to generate a first electrical signal. A multiplication operation in conventional code division multiple access (CDMA) despreading is transferred from an electrical domain to an optical domain such that a chip rate can be easily raised to 20 gigahertz (GHz) or even to 25 GHz, a maximum rate of 100 gigabits per second (Gbps) can be provided in a single wavelength, and a user requirement for high bandwidth can be met.