Embedding Low-Frequency Tone in Digital Data Streams
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Solution Overview
Problem
Existing methods for transmitting low-frequency signals over data transmission links using digital high bit-rate signals require additional hardware, such as external modulators, which is costly and not available in standard transmitter or transceiver modules.
Innovation Solution
Modulating the average power of the high bit-rate digital signal by varying the density of 'high' and 'low' bits according to the low-frequency signal, allowing the information to be encoded in the average power variations without additional hardware, using techniques like 8B/10B encoding and bit inversion, to create a modulated signal that can be demodulated using low-pass filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amplitude modulation of the optical carrier signal is used to transmit the low-frequency tone signal, then the low-frequency signal can be transmitted over the data transmission link, but additional control hardware is required which is not available in standard transmitter or transceiver modules
Solution Approach 1:
The patent uses the existing high bit-rate digital signal itself to carry the low-frequency tone signal by modulating its average power. The standard transceiver hardware processes both the high bit-rate data and the embedded low-frequency tone without requiring additional control hardware, as the tone is impressed on the signal through bit density modulation rather than traditional amplitude modulation
Solution Approach 2:
The existing transceiver hardware is made multi-functional by enabling it to simultaneously handle high bit-rate data transmission and low-frequency tone signal transmission. The standard optical modulator and detector are used for both purposes, eliminating the need for separate control hardware while maintaining transmission reliability
2Reliability
If external modulation of the optical power is used to impress the tone on the high bit-rate digital signal, then the low-frequency signal can be transmitted, but a separate and costly external modulator is required
Solution Approach 1:
The patent employs the existing optical modulator within the standard transceiver to impress the low-frequency tone on the high bit-rate digital signal by modulating the optical power based on bit density variations. This self-service approach eliminates the need for separate external modulators, reducing manufacturing cost while maintaining transmission reliability
Solution Approach 2:
The patent merges the function of high bit-rate data transmission and low-frequency tone transmission into a single optical signal. The existing optical modulator is used to combine both signals, eliminating the need for separate external modulation equipment and reducing overall system cost
3Device complexity
If the density of high bits is varied according to the low-frequency signal to modulate the average power, then no additional hardware is required, but the information cannot be detected by simply decoding the bit stream
Solution Approach 1:
The patent segments the detection process into two independent paths: one for decoding the high bit-rate data and another for extracting the low-frequency tone. The tone detection is achieved by low-pass filtering the optical signal before detection, separating it from the high bit-rate data stream. This allows standard transceiver hardware to handle both functions without increasing detection complexity
Data Source
AI summary
Disclosed is a method for transmitting a low-frequency signal over a data transmission link using a digital high bit-rate signal including the steps of creating a modulated digital high bit-rate signal the average power of which varies according to the low-frequency signal, supplying the modulated digital high bit-rate signal to a first end of the data transmission link, receiving the modulated digital high bit-rate signal at a second end of the data transmission link or at an intermediate node of the data transmission link, and detecting the low-frequency signal by low-pass filtering the received modulated digital high bit-rate signal. According to the invention, the variation of the average power of the modulated digital high bit-rate signal is effected by a variation of the density of “high” bits according to the low-frequency signal.