Optical Modulation Method for Multiplexing Services
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Solution Overview
Problem
Current optical modulation/demodulation technologies for access networks require high-cost transmitters and face challenges in band expansion and cost reduction when multiplexing services with different bit rates, as they either require multiple transmitters or suffer from reduced bandwidth due to shared transmission bands.
Innovation Solution
An optical modulation/demodulation method that uses a single transmitter to sum binary signals with bit rates that are integer multiples of a low-speed side, generating a multi-level signal for amplitude modulation, allowing multiple services to be multiplexed without increasing cost or reducing bandwidth, using a modulator and optical receiver with synchronized frequencies and amplitude adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple transmitters are used to accommodate services with different bit rates, then service versatility is improved, but device complexity and cost increase
Solution Approach 1:
A single optical transmitter is designed to handle multiple services with different bit rates by dynamically adjusting its operation mode. The transmitter can operate at different baud rates and modulation schemes, making it universal for accommodating various service requirements without needing multiple dedicated transmitters
Solution Approach 2:
The transmitter changes its operational parameters (baud rate, modulation type, symbol mapping) based on the service being transmitted. By dynamically adjusting these parameters, the same physical transmitter can adapt to different bit rate requirements, resolving the contradiction between versatility and device complexity
2Device complexity
If transmission band is shared among multiple services, then device complexity is reduced, but bandwidth availability decreases
Solution Approach 1:
The system uses time-division multiplexing where different services are transmitted in periodic time slots. The single transmitter alternates between different services at different baud rates, providing periodic transmission cycles that ensure each service receives adequate bandwidth while sharing the same physical transmission medium
Solution Approach 2:
The transmitter operates dynamically by adjusting its baud rate and modulation scheme in real-time based on which service is being transmitted. This dynamic operation allows the system to maintain high bandwidth availability for each service while using a single transmitter, resolving the contradiction between device simplicity and bandwidth performance
3Ease of manufacture
If intensity modulation with direct detection is used, then device cost is reduced, but transmission speed is limited
Solution Approach 1:
The system changes the modulation parameter from traditional intensity modulation to a specialized modulation scheme that encodes multiple bits per symbol. By adjusting the baud rate and symbol mapping parameters, the system achieves higher transmission speeds while maintaining compatibility with direct detection receivers, thus resolving the contradiction between cost and speed
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 economic realization of multiple services with different bit rates by using a simple configuration, inhibiting cost increases and bandwidth decreases during multiplexing, while maintaining efficient service accommodation in access networks.
Implementation Method 1
an optical transmitter that transmits an optical signal amplitude-modulated using the modulation signal generated by the modulator
Implementation Method 2
an optical receiver that performs photoelectric conversion of an optical signal amplitude-modulated using a modulation signal representing a combination of bits
Data Source
AI summary
An object is to provide an optical modulation/demodulation method, an optical communication system, an optical transmitting device, and an optical receiving device capable of inhibiting an increase in the cost and a decrease in the band at the time of multiplexing services. The optical transmitting device according to the present invention sums a plurality of binary signals that have bit rates having such relation that the bit rate of any higher speed side is twice or more integer multiples of a bit rate of any lower speed side, having smaller amplitude as the corresponding bit rate becomes higher and having matched rise and fall timings, and generates a multi-level signal, and modulates light from one light source. In other words, generating a multi-level signal as a modulation signal enables a plurality of services to be multiplexed by one transmitter. The optical receiving device according to an aspect of the present invention sets a plurality of thresholds that can be used for identifying all the amplitude values of the multi-level signal for an optical signal that is service-multiplexed by the optical transmitting device described above and compares an amplitude of the multi-level signal acquired by performing photoelectric conversion of the received optical signal with the plurality of thresholds. The optical receiving device determines bits of the multiplexed binary signal on the basis of a result of the comparison.