Countermeasures for idle pattern SRS interference in ethernet optical network systems
View Patent ↗Optical networks as defined by the IEEE 802.3ah standard suffer from Stimulated Raman Scattering (SRS) that causes data transmission at a first optical wavelength to interfere with broadcast video transmission at a second optical wavelength in single mode optical fibers. The problem is exacerbated when data is not being transmitted across the network; and instead, an idle pattern transmission is being transmitted in order to keep the network synchronized. The repetitive nature of the idle pattern transmission leads to the SRS optical interference effect. This optical interference effect is mitigated when countermeasures are implemented to modify the idle pattern transmissions or to transmit random data in place of the idle pattern transmissions.
1. A method for mitigating the effects of interference on video information from data signals comprising the steps of:
receiving input from a routing device;
determining whether the input comprises data and if the input comprises data, then converting the data from an electrical domain to a digital optical domain;
determining whether the input comprises one of an absence of data and an idle pattern;
generating substitute data in an electrical domain that reduces power at one or more harmonics in the electrical domain such that a concentration of power in the digital optical domain is minimized when the substitute data is converted into the digital optical domain;
in response to detecting one of an absence of data and an idle pattern, converting the substitute data from the electrical domain to the digital optical domain so that data transmission in the digital optical domain is substantially continuous when the input comprises one of an absence of data and an idle pattern; and
propagating the substitute data in the digital optical domain along with video information in an analog optical domain through a single optical waveguide, the substitute data in the digital optical domain comprising minimal concentration of optical power for reducing any optical interference between the substitute data and the video information caused by physical properties of the single optical waveguide combined with selected optical wavelengths and optical power of the substitute data and video information.
2. The method of claim 1 , wherein the step of generating substitute data further comprises generating non-repetitive random data and assigning the random data to a non-existent MAC address.
3. The method of claim 1 , wherein the step of generating substitute data further comprises alternating between different idle code pairs based upon a random variable function.
4. A method for reducing optical interference between data and video information propagated over a single optical waveguide comprising:
receiving video information in an electrical domain;
converting the video information into an analog optical domain by modulating the video information on an analog optical carrier with a first optical wavelength;
monitoring input in an electrical domain;
determining whether the input comprises data and if the input comprises data, then converting the data from an electrical domain to the digital optical domain;
determining if the input comprises one of an absence of data and an idle pattern;
generating substitute data in the electrical domain that reduces power at one or more harmonics in the electrical domain such that a concentration of energy in a digital optical domain is minimized when the substitute data is converted into the digital optical domain;
if the data comprises one of an absence of data and an idle pattern code, then converting the substitute data into the digital optical domain by modulating the substitute data on a digital optical carrier with a second optical wavelength so that data transmission in the digital optical domain is substantially continuous when the input comprises one of an absence of data and an idle pattern;
combining the analog and digital optical carriers; and
propagating the analog and digital optical carriers along the single optical waveguide, wherein the substitute data in the digital optical domain comprises minimal concentration of optical power for substantially reducing any optical interference between the analog and digital optical carriers caused by physical properties of the single optical waveguide combined with selected optical wavelengths and optical power of the substitute data and video information.
5. The method of claim 4 , wherein the step of generating substitute data further comprises generating non-repetitive random data and assigning the random data to a non-existent MAC address.
6. The method of claim 4 , wherein the step of generating substitute data further comprises using one of two idle code pairs based upon a random variable function.
7. A method for reducing optical interference between data and video information propagated over a single optical waveguide comprising:
receiving video information in an electrical domain;
converting the video information into an analog optical domain by modulating the video information on an analog optical carrier with a first optical wavelength;
generating random data assigned with a low priority that reduces power at one or more harmonics in the electrical domain such that a concentration of power in a digital optical domain is minimized when the random data is converted into the digital optical domain;
determining if any higher priority data is present for digital optical transmission;
if higher priority data is not present, then inserting the random data with the low priority for digital optical transmission so that data transmission in the digital optical domain is substantially continuous when higher priority data is not present;
converting the random data into the digital optical domain by modulating the random data on a digital optical carrier with a second optical wavelength;
combining the analog and digital optical carriers; and
propagating the analog and digital optical carriers along the single optical waveguide wherein the random data comprising minimal concentration of optical power substantially reduces any optical interference between the analog and digital optical carriers caused by physical properties of the single optical waveguide combined with selected optical wavelengths and optical power of the random data and video information.
8. The method of claim 7 , further comprising if higher priority data is present, then using the higher priority data for digital optical transmission.
9. The method of claim 7 , further comprising converting the data from the electrical domain to the digital optical domain when the data has a priority higher than the random data.
10. An optical network comprising:
a routing device for assigning data to optical taps that are coupled to one or more subscribers;
an idle pattern replacement device coupled to the routing device for determining whether data received from the routing device comprises one of an idle pattern and an absence of data, for generating a substitute idle pattern in an electrical domain when one of an idle pattern and absence of data is detected so that data transmission in a digital optical domain is substantially continuous, the substitute idle pattern reducing power at one or more harmonics in the electrical domain such that a concentration of energy in the digital optical domain is minimized when the substitute idle pattern is converted into the optical domain;
an optical transmitter for converting the substitute idle pattern from the electrical domain to the digital optical domain; and
an optical waveguide coupled to the optical transmitter for propagating the substitute idle pattern in the digital optical domain along with video information in an analog optical domain along a single optical waveguide, the substitute idle pattern comprising minimal concentration of optical power for reducing any optical interference between data and the video information caused by physical properties of the single optical waveguide combined with selected optical wavelengths and optical power of the random data and video information.
11. The optical network of claim 10 , wherein the idle pattern replacement device comprises a downstream data shift register, a replacement data shift register, and a data initializer.
12. The optical network of claim 10 , wherein the idle pattern replacement device comprises a detector for sensing the presence of real data, no data, and idle patterns.
13. The optical network of claim 12 , wherein the detector is coupled to the data initializer.