Optical power measurement in a passive optical network
A passive optical network (PON) device and method for optical power measurement along an optical transmission path supporting bidirectional propagation of downstream light and upstream light between two network elements of a PON is provided. The device includes an optical power splitter assembly extracting respective portions of the upstream and downstream light, and an upstream wavelength analyzer determining, from the extracted upstream light, an upstream spectral characteristic of the upstream light. The device also includes a processing unit determining, based on the upstream spectral characteristic, a downstream spectral characteristic of a downstream signal of interest among a plurality of downstream signals of the downstream light, and a downstream filter assembly filtering the extracted downstream light to select a portion of the downstream signal of interest. The device further includes a downstream optical power meter assembly measuring an optical power parameter of the selected portion of the downstream signal of interest.
1. A device for optical power measurement along an optical transmission path between a first network element and a second network element, the optical transmission path supporting bidirectional propagation of downstream light and upstream light, the downstream light comprising a plurality of downstream signals having mutually different central wavelengths, the device comprising:
an optical power splitter assembly configured to extract, from the optical transmission path, a portion of the downstream light and a portion of the upstream light;
an upstream wavelength analyzer configured to receive the extracted portion of the upstream light and determine therefrom an upstream spectral characteristic of the upstream light;
a processing unit coupled to the upstream wavelength analyzer and configured to determine, based on the upstream spectral characteristic, a downstream spectral characteristic of a downstream signal of interest among the plurality of downstream signals;
a downstream filter assembly configured to receive and filter the extracted portion of the downstream light to select therefrom a portion of the downstream signal of interest according to the determined downstream spectral characteristic; and
a downstream optical power meter assembly configured to measure an optical power parameter of the portion of the downstream signal of interest selected by the downstream filter assembly.
2. The device according to claim 1 , wherein the upstream wavelength analyzer is configured to determine the upstream spectral characteristic as a value of a central wavelength of the upstream light, and wherein the processing unit is configured to determine the downstream spectral characteristic as a value of a central wavelength of the downstream signal of interest.
3. The device according to claim 2 , wherein the processing unit is configured to determine the value of the central wavelength of the downstream signal of interest from reference data relating a set of possible central wavelength values for the upstream light to a set of possible central wavelength values for the downstream signal of interest.
4. The device according to claim 2 , wherein the downstream filter assembly has a passband central wavelength tunable to the determined value of the central wavelength of the downstream signal of interest.
5. The device according to claim 4 , wherein the tunable passband central wavelength is tunable in a wavelength range extending at least from 1596 nm to 1603 nm.
6. The device according to claim 1 , wherein the upstream wavelength analyzer is configured to monitor a presence of the upstream light in each of a plurality of distinct upstream spectral bands and, upon detection of the presence of the upstream light in one of the plurality of distinct upstream spectral bands, to generate a detection signal indicative of the upstream spectral characteristic.
7. The device according to claim 6 , wherein the plurality of distinct upstream spectral bands comprises a first upstream spectral band ranging at least from 1260 nm to 1280 nm, a second upstream spectral band ranging at least from 1290 nm to 1330 nm, and a third upstream spectral band ranging at least from 1524 nm to 1625 nm.
8. The device according to claim 6 , wherein the detection signal is indicative of a value of a central wavelength of the upstream light, the downstream filter assembly has a tunable passband central wavelength, and the processing unit is configured to determine a value of a central wavelength of the downstream signal of interest based on the value of the central wavelength of the upstream light, the tunable passband central wavelength of the downstream filter assembly being tuned to the determined value of the central wavelength of the downstream signal of interest.
9. The device according to claim 6 , wherein the upstream wavelength analyzer comprises:
an upstream filter assembly configured to filter the extracted portion of the upstream light according to a plurality of passbands corresponding to the plurality of distinct upstream spectral bands; and
an upstream detection assembly comprising a plurality of upstream detection circuits, each detection circuit being configured to receive a filtered signal from the upstream filter assembly in a respective one of the plurality of passbands and to generate the detection signal indicative of the upstream spectral characteristic upon detection of the presence of the upstream light in the respective one of the plurality of passbands.
10. The device according to claim 1 , wherein:
the downstream filter assembly is configured to spectrally split the extracted portion of the downstream light according to a plurality of downstream spectral bands; and
the downstream optical power meter assembly comprises a plurality of power meter devices, each power meter device being configured to measure an optical power parameter of a filtered signal received from the downstream filter assembly in a corresponding one of the downstream spectral bands, one of the optical power parameters measured by the power meter devices corresponding to the optical power parameter of the portion of the downstream signal of interest.
11. The device according to claim 10 , wherein the processing unit is configured to identify, based on the determined downstream spectral characteristic, the optical power parameter corresponding to the optical power parameter of the portion of the downstream signal of interest.
12. The device according to claim 10 , wherein:
the downstream signal of interest and the downstream spectral characteristic are respectively a first downstream signal of interest and a first downstream spectral characteristic;
the processing unit is configured to determine, based on the upstream spectral characteristic, an additional downstream spectral characteristic of an additional downstream signal of interest among the plurality of downstream signals, the first and the additional downstream signals of interest lying in different ones of the downstream spectral bands; and
the optical power parameter measured by another one of the power meter devices corresponds to an optical power parameter of a portion of the additional downstream signal of interest.
13. The device according to claim 10 , wherein the plurality of downstream spectral bands comprises a first downstream spectral band ranging at least from 1575 nm to 1580 nm, a second downstream spectral band ranging at least from 1480 nm to 1500 nm, a third downstream spectral band ranging at least from 1550 nm to 1560 nm, and a fourth downstream spectral band ranging at least from 1596 nm to 1603 nm.
14. The device according to claim 1 , comprising first and second connector ports connected to the optical power splitter assembly for serially inserting the device in the optical transmission path between the first and the second network elements.
15. A device for optical power measurement along an optical transmission path between a first network element and a second network element, the optical transmission path supporting bidirectional propagation of downstream light and upstream light, the downstream light comprising a plurality of downstream signals having mutually different central wavelengths, the device comprising:
an optical power splitter assembly configured to extract, from the optical transmission path, a portion of the downstream light and a portion of the upstream light;
an upstream wavelength analyzer configured to receive the extracted portion of the upstream light from the optical power splitter assembly and to measure therefrom a value of a central wavelength of the upstream light;
a downstream filter assembly configured to receive and filter the extracted portion of the downstream light to select therefrom a portion of the downstream signal of interest, the downstream filter assembly having a tunable passband central wavelength;
a processing unit coupled to the upstream wavelength analyzer and the downstream filter assembly, the processing unit being configured to determine, from the measured value of the central wavelength of the upstream light, a value of a central wavelength of a downstream signal of interest among the plurality of downstream signals, the tunable passband central wavelength of the downstream filter assembly being tuned to the determined value of the central wavelength of the downstream signal of interest, thereby selecting the portion of the downstream signal of interest; and
a downstream optical power meter assembly configured to measure an optical power parameter of the portion of the downstream signal of interest selected by the downstream filter assembly.
16. The device according to claim 15 , wherein the tunable passband central wavelength of the downstream filter assembly is tunable in a wavelength range extending at least from 1596 nm to 1603 nm.
17. A method for optical power measurement along an optical transmission path between a first network element and a second network element, the optical transmission path supporting bidirectional propagation of downstream light and upstream light, the downstream light comprising a plurality of downstream signals having mutually different central wavelengths, the method comprising:
extracting, from the optical transmission path, a portion of the downstream light and a portion of the upstream light;
determining, from the extracted portion of the upstream light, an upstream spectral characteristic of the upstream light;
determining, based on the upstream spectral characteristic, a downstream spectral characteristic of a downstream signal of interest among the plurality of downstream signals;
filtering the extracted portion of the downstream light to select therefrom a portion of the downstream signal of interest according to the determined downstream spectral characteristic; and
measuring an optical power parameter of the selected portion of the downstream signal of interest.
18. The method according to claim 17 , wherein determining the upstream spectral characteristic comprises measuring a value of a central wavelength of the upstream light, and wherein determining the downstream spectral characteristic comprises determining a value of a central wavelength of the downstream signal of interest.
19. The method according to claim 18 , wherein determining the value of the central wavelength of the downstream signal of interest comprises accessing reference data relating a set of possible central wavelength values for the upstream light to a set of possible central wavelength values for the downstream signal of interest.
20. The method according to claim 18 , wherein filtering the extracted portion of the downstream light comprises tuning a passband center wavelength to the determined value of the central wavelength of the downstream signal of interest.
21. The method according to claim 20 , wherein tuning the passband center wavelength comprises tuning the passband center wavelength in a wavelength range extending at least from 1596 nm to 1603 nm.
22. The method according to claim 17 , wherein:
filtering the extracted portion of the downstream light comprises spectrally splitting the extracted portion of the downstream light into a plurality of downstream spectral bands; and
measuring the optical power parameter of the portion of the downstream signal of interest comprises measuring an optical power parameter of a filtered signal in each of the downstream spectral bands, one of the optical power parameters measured by the power meter devices corresponding to the optical power parameter of the portion of the downstream signal of interest.