N-input receiver: RFoG OBI mitigation with retransmission
A multimode combiner or coupler (MMC) may combine the inputs into a larger core multimode fiber. The multimode combiner may be combined with a re-transmitting laser for detecting and re-transmitting signals. Thus, the multi-mode combiner may detect and combine input signals, and then retransmit the detected, combined signal. The detection can be implemented with multiple single mode fibers to small single mode detectors or a multi-mode coupler with a larger multi-mode detectors. In embodiments of the MMC, a bi-directional optical splitter/combiner includes a transmitter for re-transmitting an RF signal received at a receiver, a first wave division multiplexer (WDM) combiner combining the output of the first transmitter in an upstream direction to a downstream signal in a downstream direction, and a second WDM combiner combining split downstream signals in the downstream direction with upstream signals received via at least two optical fiber inputs.
1. A bi-directional optical splitter/combiner functioning passively in a downstream direction and active in an upstream direction, the bi-directional optical splitter/combiner comprising:
at least two optical fiber inputs for receiving upstream signals;
at least one optical receiver for receiving a radio frequency over fiber (RFof) modulated signal, the at least one optical receiver including at least one optical detector that uses a photo detector having a size configured to detect and retransmit at an optical receiver output a signal that carries the total optical power received from a plurality of optical signals having different wavelengths, and without optical beat interference occurring in the retransmitted signal;
a first optical transmitter for receiving the RFof modulated signal from the optical receiver output and re-transmitting the RFof modulated signal from the at least one receiver, the first optical transmitter providing an output;
a first wave division multiplexer (WDM) optical combiner combining the output of the first optical transmitter in an upstream direction to a downstream optical signal in a downstream direction;
an optical splitter for splitting the downstream optical signal to provide at least two split optical downstream signals; and
a second WDM optical combiner combining each split optical downstream signal in the downstream direction with the upstream signals received by the at least two optical fiber inputs.
2. The bi-directional optical splitter/combiner of claim 1 , further comprising:
at least one single mode to multi-mode optical combiner combining at least two signals received at the at least two optical fiber inputs to a multi-mode fiber output; and
the at least one optical detector formed large enough to encompass an entire field of combined beams from the multi-mode fiber output.
3. The bi-directional optical splitter/combiner of claim 1 , further comprising wavelength selective optical components for directing upstream light at a first wavelength and passing downstream light at a second wavelength.
4. The bi-directional optical splitter/combiner of claim 1 , further comprising a multi-mode optical combiner (MMC) for combining inputs from one or more optical fibers for transmitting a multimode signal into a multimode fiber sufficiently large to transmit all light provided at the input to the MMC, the multimode fiber having a core larger than a single-mode fiber to preserve the light in the larger core multimode fiber.
5. The bi-directional optical splitter/combiner of claim 4 , wherein the at least one optical detector is large enough to provide a detector output signal to an amplifier, the amplifier driving the first transmitter and sending a signal to the first WDM optical combiner connected to a fiber extending to a headend.
6. The bi-directional optical splitter/combiner of claim 4 , wherein the at least one optical detector has a size large enough for detecting the multimode fiber signal from the larger core multimode fiber and a corresponding capacitance related to the size of the optical detector.
7. The bi-directional optical splitter/combiner of claim 1 , further comprising at least one optical receiver for receiving wavelengths sent upstream by optical network units that terminate radio frequency over glass (RFoG) at a customer premises with transmit and receive functions.
8. The bi-directional optical splitter/combiner of claim 1 , transmitting wavelengths downstream to optical network units that terminate radio frequency over glass (RFoG) at a customer premises with transmit and receive functions.
9. The bi-directional optical splitter/combiner of claim 8 , further comprising an erbium doped fiber amplifier (EDFA) that amplifies the downstream wavelengths.