Flexible wavelength selective switch fabric with arbitrary add and drop capability
View Patent ↗A flexible wavelength switch fabric may be implemented with multiple groups of reconfigurable blocking filters or with multiple multi-in, single out wavelength selective switches. The behaviors of reconfigurable blocking filters are individually settable, such as channel blocking, channel spacing, transmission rate, and default blocking state. Add and drop taps may be added to provide arbitrary add/drop capability. Optical splitters/combiners used may be tunable so that insertion losses may be minimized for the overall network.
1. A method of optimizing a Wavelength Selective Switch (“WSS”) fabric, comprising:
providing a plurality of optical splitters, each optical splitter receiving a corresponding input optical signal from a corresponding external source and splitting the received signal into a plurality of split signals;
providing a plurality of reconfigurable blocking filters (RBF) grouped in groups of RBFs, each group possessing a plurality of optical inputs, receiving a split signal from the optical splitters, and optical outputs outputting the filtered versions of the split signals;
providing a plurality of optical combiners, wherein each combiner receives the plurality of the filtered versions of the split signals from the plurality of optical outputs from each group of the RBFs, combines the received plurality of the filtered versions of the split signals and outputs the combined signal to external optical components; and
optimizing the WSS flexibility by adjusting transmission profiles of the RBFs in accordance with control signals received from external controllers;
where transmission profile of at least one RBF is adjusted to be seamless, with no gaps in channel wavelength spacing between adjacent channels, small attenuation, and with small group delay ripple to support optical signals with multiple channel spacings and multiple transmission rates.
2. The method of claim 1 , where the adjusting of the transmission profiles of the RBFs in accordance to control signals received from external controllers is achieved dynamically where the transmission profile of the RBFs is changed without stopping the operations of the RBFs.
3. The method of claim 1 , where the attenuation is less than 0.2 dB.
4. The method of claim 1 , where the group delay ripple is less than 3 ps.
5. The method of claim 1 , where the optical signals with multiple channel spacings include channel spacings of: 25 GHz, 50 GHz, 100 GHz, and any combination of the listed channel spacings.
6. The method of claim 1 , where the optical signals with multiple transmission rates include transmission rates of: 2.5 Gb/s, 10 Gb/s, 40 Gb/s, and any combination of the listed transmission rates.
7. A method of improvement of reliability of a WSS fabric, comprising:
providing a plurality of optical splitters where each optical splitter is configured to receive a corresponding input optical signal from a corresponding external source and to split the received signal into a plurality of split signals,
providing a plurality of reconfigurable blocking filters (RBF) grouped in groups of RBFs, each group possessing plurality of optical inputs, configured to receive a split signal from the optical splitters, and optical outputs to output the filtered versions of the split signals, and
providing a plurality of optical combiners wherein each combiner is configured to receive the plurality of the filtered versions of the split signals from the plurality of optical outputs from each group of the RBFs, combine the received plurality of the filtered versions of the split signals and output the combined signal to external optical components;
wherein the improvement of reliability is achieved by setting of all RBFs default states to be “blocking” to minimizes the impact of failure of RBFs in the WSS fabric.
8. A method of achieving an arbitrary drop of any chosen channel in a WSS fabric with no changes in hardware, said method comprising:
providing a plurality of optical splitters where each optical splitter is configured to receive a corresponding input optical signal from a corresponding external source and to split the received signal into a plurality of split signals;
providing a plurality of reconfigurable blocking filters (RBF) grouped into groups of RBFs, each group possessing plurality of optical inputs, configured to receive a split signal from the optical splitters, and optical outputs to output the filtered versions of the split signals; and
providing a plurality of optical combiners wherein, each combiner is configured to receive the plurality of the filtered versions of the split signals from the plurality of optical outputs from each group of the RBFs, combines the received plurality of the filtered versions of the split signals and output the combined signal to external optical components;
wherein the arbitrary drop of any chosen channel is achieved by adjusting transmission profiles of any group RBFs in accordance to control signals received from external controllers to block any chosen channel and transmit no signal in any chosen channel in the filtered version of the split signals to the optical combiner.
9. The method of claim 8 , where the adjusting of the transmission profiles of the RBFs in accordance to control signals received from external controllers is achieved dynamically where the transmission profile of the RBFs is changed without stopping the operations of the RBFs.