Precisely capturing time of an event in processing circuitry of an optical module
An optical module includes a receiver configured to receive an optical signal, and processing circuitry configured to obtain data associated with the optical signal, periodically generate a reference signal, at a first point in the processing circuitry, each reference signal has an associated time, detect a significant event requiring a timestamp at a second point in the processing circuitry, and utilize a corresponding reference signal and its associated bit offset to determine the timestamp for the significant event. The first point is after the optical signal is converted to the data as bits, but where there is no data awareness.
1 . An optical module comprising a receiver configured to receive an optical signal, and processing circuitry configured to:
obtain data associated with the optical signal,
periodically generate a reference signal, at a first point in the processing circuitry where bits are first available from the receiver and prior to electrical processing that provides protocol awareness, each generated reference signal has an associated reference time,
detect a significant event requiring a timestamp at a second point in the processing circuitry, and
identify a latest one of the periodically generated reference signals preceding the significant event, determine a bit offset representing a number of bits between the latest reference signal and the significant event, and utilize the reference time associated with the latest reference signal and the bit offset to determine the timestamp for the significant event.
2 . The optical module of claim 1 , wherein the first point is after the optical signal is converted to the data as bits, but where there is no protocol awareness.
3 . The optical module of claim 1 , wherein there is variable delay between the first point and the second point based on data modification in the processing circuitry, such that the latest reference signal and the bit offset representing the number of bits between the latest reference signal and the significant event is utilized to determine an adjustment of the timestamp for compensation thereof.
4 . The optical module of claim 1 , wherein the processing circuitry is further configured to
implement any of clock domain crossing, gearboxing, adding or dropping bits in the data, protocol processing, and Forward Error Correction (FEC) processing between the first point and the second point.
5 . The optical module of claim 1 , wherein the processing circuitry is further configured to
send the periodically generated reference signal with the data from the first point to the second point such that the periodically generated reference signal propagates alongside the data through the processing circuitry and experiences the same delay as the data associated with the significant event.
6 . The optical module of claim 5 , wherein there is variable delay between the first point and the second point based on data modification in the processing circuitry, including at least one of clock domain crossing, gearboxing, or adding or dropping bits, and wherein the periodically generated reference signal experiences a same variable delay as the significant event, enabling compensation thereof.
7 . The optical module of claim 1 , wherein the processing circuitry is further configured to
maintain one or more bit counters and utilize the one or more bit counters to account for a bit offset representing a number of bits between the latest reference signal and the significant event.
8 . The optical module of claim 1 , wherein the significant event is based on Precision Time Protocol (PTP).
9 . The optical module of claim 1 , wherein the optical signal is modulated using coherent modulation.
10 . The optical module of claim 1 , wherein the optical signal is modulated using Pulse Amplitude Modulation (PAM).
11 . A method comprising steps of:
obtaining data associated with an optical signal;
periodically generating a reference signal, at a first point in processing circuitry where bits are first available from the receiver and prior to electrical processing that provides protocol awareness, each generated reference signal has an associated reference time;
detecting a significant event requiring a timestamp at a second point in the processing circuitry; and
identifying a latest one of the periodically generated reference signals preceding the significant event, determine a bit offset representing a number of bits between the latest reference signal and the significant event, and utilize the reference time associated with the latest reference signal and the bit offset to determine the timestamp for the significant event.
12 . The method of claim 11 , wherein the first point is after the optical signal is converted to the data as bits, but where there is no protocol awareness.
13 . The method of claim 11 , wherein there is variable delay between the first point and the second point based on data modification in the processing circuitry, such that the latest reference signal and the bit offset representing the number of bits between the latest reference signal and the significant event is utilized to determine an adjustment of the timestamp for compensation thereof.
14 . The method of claim 11 , wherein the steps further include
implementing any of clock domain crossing, gearboxing, adding or dropping bits in the data, protocol processing, and Forward Error Correction (FEC) processing between the first point and the second point.
15 . The method of claim 11 , wherein the steps further include
sending the periodically generated reference signal with the data from the first point to the second point such that the periodically generated reference signal propagates alongside the data through the processing circuitry and experiences the same delay as the data associated with the significant event.
16 . The method of claim 15 , wherein there is variable delay between the first point and the second point based on data modification in the processing circuitry, including at least one of clock domain crossing, gearboxing, or adding or dropping bits, and wherein the periodically generated reference signal experiences a same variable delay as the significant event, enabling compensation thereof.
17 . The method of claim 11 , wherein the steps further include
maintaining one or more bit counters and utilizing the one or more bit counters to account for a bit offset representing a number of bits between the latest reference signal and the significant event.
18 . The method of claim 11 , wherein the significant event is based on Precision Time Protocol (PTP).
19 . The method of claim 11 , wherein the optical signal is modulated using coherent modulation.
20 . The method of claim 11 , wherein the optical signal is modulated using Pulse Amplitude Modulation (PAM).