Coded Pilot Tone Signal for Reliable Optical Power Monitoring
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Solution Overview
Problem
Conventional pilot tone data modulation using on/off keying (OOK) in optical networks is ineffective for detecting power during successive zero data bits, leading to unreliable power measurement and slow loss of signal detection, as there is no power in the pilot tone signal for each zero bit, making it indistinguishable from actual signal loss.
Innovation Solution
Encoding data bit streams with coded sequences for both '1' and '0' bits, where each bit duration includes a repeated portion of the code, allowing for reliable detection using overlapping measurement windows and cross-correlation, ensuring power detection during both bit types and enabling fast loss of signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If on/off keying (OOK) modulation is used for pilot tone data modulation, then the modulation scheme is simple and easy to implement, but the power in the pilot tone signal is zero for each zero bit, making it impossible to detect the presence of the high speed optical signal during zero bits
Solution Approach 1:
The patent changes the modulation parameter by using a coded modulation scheme instead of simple OOK. Each data bit is represented by a coded sequence where both '0' and '1' bits have non-zero power levels, allowing continuous detection of the pilot tone signal presence regardless of the data bit value.
Solution Approach 2:
Instead of using zero power to represent zero bits (OOK), the patent inverts the approach by ensuring all bits have non-zero power. The information is encoded in the pattern and timing of the coded sequences rather than the presence/absence of power, enabling reliable signal detection during both zero and one bits.
2Device complexity
If conventional OOK modulation is used, then the implementation is simple, but the loss of signal detection is slow and unreliable because zero bits produce no power in the pilot tone signal
Solution Approach 1:
The patent applies preliminary coding to the data bits before modulation, creating coded sequences that maintain non-zero power throughout. This preliminary preparation ensures that the pilot tone signal continuously indicates signal presence, enabling immediate detection of signal loss without waiting for specific bit patterns.
Solution Approach 2:
The coded modulation scheme provides continuous feedback about signal presence through the persistent non-zero power levels. The receiver can continuously monitor the pilot tone power and immediately detect when the signal is lost, as opposed to OOK where detection is intermittent and unreliable during zero bits.
3Ease of operation
If OOK modulation is used, then the system is simple to operate, but accurate power measurement cannot be performed during zero bits since there is no power in the pilot tone signal
Solution Approach 1:
The patent changes the power parameter by designing coded sequences where both '0' and '1' bits produce non-zero power levels in the pilot tone signal. This allows the receiver to continuously measure pilot tone power and accurately determine signal presence and power levels regardless of the underlying data bit values.
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 provides accurate power measurement and reliable data detection, improving pilot tone data rate and enabling quick loss of signal detection, even during zero bits, thus enhancing optical performance monitoring in optical networks.
Implementation Method 1
encoding the pilot tone signal with the coded data stream to produce a coded pilot tone signal
Implementation Method 2
detecting a coded pilot tone signal
Data Source
AI summary
An aspect of the disclosure provides methods and systems for encoding a data bit stream onto a pilot tone signal. Another aspect of the disclosure provides method and systems for pilot tone detection. In both, a coded pilot tone signal is encoded using a code sequence m1 for each bit value of 1 (b1) and a code sequence m0 for each bit value of 0 (b0) of a data bit stream including pilot tone data bit values of 1 (b1) and bit values of 0 (b0), with each code sequence having multiple coding bits in the duration of each bit. Pilot tone detection can further include decoding each code sequence of the coded pilot tone signal using a plurality of successive overlapping measurement windows. In some embodiments each measurement window is of the same duration, being of the duration of each code sequence, and detecting each code sequence comprises selecting one of the plurality of measurement windows to represent a complete code sequence.