Programmable optical add-drop multiplexer for communication network having a bi-directional optical filter

Abstract

A programmable OADM (601) for a communication network having a bi-directional optical fiber is provided. The OADM includes a bi-directional amplifier (603) including first (701a) and second (701b) three-port wavelength selection devices configured to route a downstream channel and / or an upstream channel based on a wavelength of the downstream channel or upstream channel. The OADM further includes a power splitter / combiner (605) having (i) a common port and (ii) a plurality of power splitter / combiner ports. The OADM further includes at least one tunable add-drop component (607) including a common add / drop port, a drop port configured to drop a defined wavelength from the downstream channel applied to the common add / drop port, and an add port configured to add to the common add / drop port an assigned wavelength from the upstream channel when the upstream channel is applied to the add port. A bi-directional amplifier (603) is also disclosed.

Description

[0001] PROGRAMMABLE OPTICAL ADD-DROP MULTIPLEXER FOR COMMUNICATION NETWORK HAVING A BI-DIRECTIONAL OPTICAL FILTER

[0002] TECHNICAL FIELD

[0003] The present disclosure relates generally to a programmable optical add-drop multiplexer (OADM) and a bi-directional amplifier for a communication network having a bi-directional optical fiber, and related apparatuses and methods.

[0004] BACKGROUND

[0005] The evolution of fifth generation (5G) to 5G-Beyond and sixth generation (6G) may further enforce a need to use Dense Wavelength Division Multiplexing (DWDM) technology for high bandwidth and low latency requirements. The evolution of a radio access network (RAN) in a centralized location and a cloud RAN also may require using DWDM in an access segment to connect several antenna sites to the centralized site (e.g., a central office of an operator(s)). For such a deployment, several infrastructures may be used to connect antennas (e.g., chains and tree). In some approaches, the DWDM technology may be used in an overlay on already installed passive optical network (PON) infrastructure.

[0006] SUMMARY

[0007] A programmable OADM for a communication network having a bi-directional optical fiber is provided. The OADM includes a bi-directional amplifier comprising a first and a second three-port wavelength selection device respectively configured to route a downstream channel and / or an upstream channel from the bi-directional optical fiber based on a wavelength of the respective downstream channel or upstream channel. The OADM further includes a power splitter / combiner having (i) a common port connected to an output / input of the bi-directional amplifier and (ii) a plurality of power splitter / combiner ports. The OADM further includes at least one tunable add-drop component comprising a common add / drop port connected to a respective one of the plurality of power splitter / combiner ports, a drop port configured to drop a defined wavelength from the downstream channel applied to the common add / drop port, and an add port configured to add to the common add / drop port an assigned wavelength from the upstream channel when the upstream channel is applied to the add port. A bi-directional amplifier for a communication network having a bi-directional optical fiber is provided. The bi-directional amplifier includes a first three-port wavelength selection device; and a second three-port wavelength selection device. The first and the second three- port wavelength selection devices are respectively configured to route a downstream channel and / or an upstream channel from the bi-directional optical fiber based on a wavelength of the respective downstream channel or upstream channel.

[0008] Potential advantages provided by various embodiments of the present disclosure may include that the architecture of the OADM may hinder reflections and may be low loss; and / or that the bi-directional amplifier may counteract or reduce reflection effects based on the properties of three-port wavelength selection devices in combination with an appropriate mapping (e.g., programming) for downstream and upstream flows.

[0009] BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate certain non-limiting embodiments of inventive concepts. In the drawings:

[0011] Figure 1 is a schematic diagram illustrating a fronthaul network architecture in accordance with some embodiments of the present disclosure;

[0012] Figure l is a block diagram illustrating a bi-directional amplifier;

[0013] Figure 3 is a schematic diagram illustrating optical signals and reflected signals in the bi-directional amplifier of Figure 2;

[0014] Figure 4 is a block diagram illustrating another bi-directional amplifier;

[0015] Figure 5 is a schematic diagram illustrating optical signals and reflected signals in the bi-directional amplifier of Figure 4;

[0016] Figure 6 is a block diagram illustrating a bi-directional amplifier in accordance with some embodiments of the present disclosure;

[0017] Figure 7 is a block diagram illustrating a bi-directional amplifier in accordance with some embodiments of the present disclosure;

[0018] Figure 8 is a schematic diagram illustrating optical signals and reflected signals travelling in a bi-directional amplifier in accordance with some embodiments of the present disclosure; Figure 9 is a schematic diagram illustrating optical signals and reflected signals travelling in a bi-directional amplifier in accordance with some embodiments of the present disclosure; and

[0019] Figures 10A and 10B are block diagrams of a tunable add-drop component in accordance with some embodiments of the present disclosure.

[0020] DETAILED DESCRIPTION

[0021] The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which examples of embodiments of inventive concepts are shown. Inventive concepts may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of present inventive concepts to those skilled in the art. It should also be noted that these embodiments are not mutually exclusive. Components from one embodiment may be tacitly assumed to be present / used in another embodiment.

[0022] The following description presents various embodiments of the disclosed subject matter. These embodiments are presented as teaching examples and are not to be construed as limiting the scope of the disclosed subject matter. For example, certain details of the described embodiments may be modified, omitted, or expanded upon without departing from the scope of the described subject matter.

[0023] The following explanation of potential problems with some approaches is a present realization as part of the present disclosure and is not to be construed as previously known by others.

[0024] For bi-directional transmission on a single optical fiber, programmable (e.g., remotely reconfigurable via computing device) devices and tunable transceivers may be needed, e.g., to save costs of inventory and operations in the field. Figure 1 is a schematic diagram illustrating an example fronthaul network architecture 100 in accordance with some embodiments of the present disclosure. In a central office 107, a multipl exer / demultiplexer (Mux / DeMux) device 109 routes input wavelengths in a wavelengths comb (referred to herein as a downstream comb) at the output optical fiber 113. Mux / DeMux 109 also extracts individual wavelengths from an input wavelength comb (referred to herein as an upstream comb) and routes an extracted wavelength(s) on one assigned output fiber. A single feeder optical fiber 113 connects the central office 107 with an optical distribution node (ODN) 105 where a 1 :R power spliter replicates the arriving DWDM downstream comb on each of the R output fibers 115a-115n and combines the R upstream combs, coming from the remote antenna sites 103a-103n on a communication port toward the central office 107. It is noted that in Figure 1, antenna sites 103b, 103d, and 103e are not annotated but correspond to the antenna sites connected to the optical add-drop multiplexers (OADM) 101b, 101 d, and lOle, respectively.

[0025] At the respective antenna sites 103a-103n, a respective OADM lOla-lOln routes a sub-set of wavelengths of the incoming downstream comb toward assigned local receivers and adds the sub-set of wavelengths, locally generated at the respective antenna sites 103a- 103n, to the outgoing upstream comb.

[0026] To reduce a number of equipment variants due to a high number of wavelengths, a tunable optical transmitter and low-cost programmable OADM may not only simplify installation procedures, but also may allow for remote, automatic programmable network configuration (e.g., via a computing device). While the OADM lOla-lOln in Figure 1 are illustrated at antenna sites 103a-103n, one or more of the OADMs lOla-lOln may be located at a remote site in the field or at a central office (e.g., central office 107). For example, to reduce inventory costs, it may be useful to provide OADMs where the wavelengths assigned to an add and / or drop port of the OADM can be selected / configured via dynamic remote programming of the OADM.

[0027] Continued improvement in transmission and switching technologies / techniques may be expected in order to reduce operating costs (e.g., drastically reduce OpEx costs). A programmable OADM(s) in a terrestrial metropolitan and / or core network may use a microelectromechanical system (MEMS) and / or liquid crystal technologies whose cost may hardly scale down to technological-economic feasibility of access networks. See e.g., F. Cavaliere, L. Giorgi and L. Poti, "Transmission and Switching Technologies for 5G Transport Networks," 2018 IEEE Optical Interconnects Conference (OI), Santa Fe, NM, 2018, pp. 47- 48. An approach for a design of mini-remote OADMs (ROADMs) using an integrated reconfigurable silicon photonics switch based on mirroring resonators has been discussed. See e.g., F. Testa et al., "Integrated Reconfigurable Silicon Photonics Switch Matrix in IRIS Project: Technological Achievements and Experimental Results," in Journal of Lightwave Technology, vol. 37, no. 2, pp. 345-355, 15 Jan.15, 2019. In such an approach, however, the link and the mini-ROADM losses may need to be compensated by suitable amplification techniques for practical use. Moreover, it may be beneficial to have an OADM that supports the bidirectional transmission of wavelengths combs in the same optical fiber, and that is tunable. As used herein, the terms “tunable” refers to a capability to set tunable wavelengths for add, drop, and passthrough channels dynamically via programming the OADM (e.g., via remote programming of the OADM with a computing device).

[0028] Presently, bidirectional OADMs may be based on optical filters but with several implementation variants depending on a number and set of added / dropped wavelengths, and number of input and output optical ports. This may lead to a large number of product variants, where the product variants each may be deployed in small volumes. To avoid such a market fragmentation and to benefit from larger economies of scale, it may be beneficial to have a single programmable OADM that is compatible with all configurations of Figure 1 (as an example architecture) that includes the following features:

[0029] Capability to add and drop an arbitrary subset of wavelengths among those received and generated at the central office 107.

[0030] Compatibility with chain, point-to-multipoint, or mixed topology networks as illustrated in the example communication network of Figure 1.

[0031] Low cost, for example on the order of the cost of a fixed add / drop module (e.g., a module that is capable to add and drop a fixed small number of predetermined wavelengths (e.g., four predetermined wavelengths).

[0032] Compatibility with bidirectional transmission system at each line port.

[0033] In some approaches, current fixed optical add drop multiplexers (FOADM) may meet features ii. and iii ., but may not meet features i. and iv.

[0034] In another approach, current reconfigurable OADMs based on wavelength selective switches (WSS) may meet features i. and ii. while adding expensive and bulky ad hoc equipment, but may not meet features iii. and iv.

[0035] In another approach, ROADMs based on silicon photonics may meet feature i. with some limitations, and features ii. and iii., but may not meet feature iv.

[0036] Thus, none of these approaches meet feature iv.

[0037] Additionally, it may be possible to use several network infrastructures to connect an antenna with the base band, such as trees, chains, and their combination. With the growth of the channel data rate (which presently may be, e.g., about 25Gbps intensity modulation-direct detection (IM-DD)), future higher capacity may benefit from the introduction of optical amplification in the RAN as well to help compensate for the insertion loss of an ODN and OADM(s), which may help to provide an appropriate level of optical power at the receiver. In a network scenario based on a single optical fiber between a central office and an antenna site, a bidirectional optical amplifier 201 (BiDi-amplifier) as illustrated in Figure 2 may be used to try to counteract the network losses.

[0038] The BiDi-amplifier 201 is based on two optical amplifiers (OAs), OA 205a and OA 205b, and two optical circulators, circulator 203a and circulator 203b. The optical circulators 203a, 203b are directi on- selective devices; and they route the signals received on one of the ports 203a, 203b, 203c or on one of the ports 207a, 207b, 207c to another port of circulator 203a or circulator 207 depending on the signal’s direction.

[0039] Figure 3 is a schematic diagram illustrating optical signals and reflected signals in the bi-directional amplifier 201 of Figure 2. As referred to herein, the phrase “reflected downstream” (R-D) signals refers to undesired signals that are generated by optical reflections of signals travelling in the opposite direction (downstream in this case) with respect to upstream flow and that follow an upstream signal in the upstream direction; and the phrase “reflected upstream” (R-U) signals refers to undesired signals that are generated by optical reflections of signals travelling in the opposite direction (upstream in this case) with respect to downstream flow and that follow a downstream signal in the downstream direction.

[0040] As shown in Figure 3, signals that flow into the BiDi-amplifier 201 are illustrated. Starting from line 101a port (also referred to herein as “Line West” port), both the incoming upstream (up) comb and reflected downstream (R-D) comb arrive to the port 203a of circulator 203 where they are routed to the port 203b and sent to the optical amplifier (OA) 205a. At OA 205a, the upstream and R-D signals are amplified and sent to the port 207a of circulator 207. Circulator 207 routes the two combs (upstream and R-D) on its port 207b, and the upstream and the R-D signals come out of the BiDi amplifier 201 via 101b port (also referred to herein as the “Line East” port).

[0041] In the opposite direction, both the incoming downstream (down) comb and reflected upstream (R-U) comb applied to the line 101b port (also referred to herein as “Line East” port) arrive to the port 207b of circulator 207 where they are routed to the port 207c and sent to the OA 205b. At OA 205b, the downstream and R-U signals are amplified and sent to the port 203c of circulator 203. Circulator 203 routes the two combs on its port 403a, and the downstream and R-U signals come out of the BiDi amplifier 201 via the line 101a port. While the terms “Line West” and “Line East” are used herein to refer to opposite directions, the opposite directions of embodiments of the present disclosure are not limited to West-East directions and may include any opposite directions.

[0042] Figure 4 is block diagram illustrating an implementation variation of bi-directional amplifier 201 where circulators 203 and 207 of Figure 2 are substituted in Figure 4 with two 1 :2 power splitters 403 and 407 (e.g., two 3dB splitters) and two optical isolators 405a, 405b.

[0043] The architecture of the BiDi amplifier 201 of Figure 4 works the same as the BiDi amplifier 201 of Figure 2, as illustrated in Figure 5. As shown in Figure 5, signals that flow into the BiDi-amplifier 201 are illustrated. Starting from line 101a port, both the incoming upstream (up) comb and reflected downstream (R-D) comb arrive to the port 403a of splitter 403 where they are routed to the port 403b and sent to the OA 205a. At OA 205a, the upstream and R-D signals are amplified and sent to the port 407a of splitter 407. Splitter 407 routes the two combs (upstream and R-D) on its port 407b, and the upstream and the R-D signals come out of the BiDi amplifier 201 via the line 101b port.

[0044] In the opposite direction, both the incoming downstream (down) comb and reflected upstream (R-U) comb applied to the line 101b port arrive to the port 407a of splitter 407 where they are routed to the port 407c and sent to the OA 205b. At OA 205b, the downstream and R-U signals are amplified and sent to the port 403c of splitter 403. Splitter 403 routes the two combs on its port 403a, and the downstream and R-U signals come out of the BiDi amplifier 201 via 101a port.

[0045] Both architectures of the BiDi-amplifier 201 shown in Figures 2 and 4 may suffer from effects of the reflections of the optical signals including, without limitation, that the reflections that can be concentrated (e.g., due to device return loss or fiber connectors return loss) or distributed (e.g., due to Rayleigh or Brillouin backscattering). Using a single optical fiber and bi-directional communication, the reflections may increase noise present on the communication channel in both directions. In some cases, the power’s reflections may become comparable with those of the signals, which may cause a situation that is not tolerable. For example, this may happen using either architecture of the BiDi-amplifier 201 in a communication network because the reflections may be amplified inside the BiDi amplifier 201 as well as the wanted signal.

[0046] Thus, it may be advantageous to have an architecture of a BiDi amplifier that may reduce or cut the reflections so as to avoid their amplification and back propagation in a communication network. Various embodiments of the present disclosure may provide solutions to these and other potential problems. Various embodiments of the present disclosure provide a programmable OADM for a bi-directional transmission communication network where the programmability is compatible with chain, point-to-multipoint, and / or mixed topologies. In some embodiments, the OADM can be configured to be a passthrough node or a termination node, as discussed further herein.

[0047] Potential advantages provided by various embodiments of the present disclosure may include that the OADM may amplify optical signals that travel in an opposite direction on the same optical fiber; may be a low loss OADM for application in communication networks characterized by high concentrated insertion loss; may reduce and / or cancel reflections of channels travelling in the opposite direction and, thus, may avoid or reduce their amplification and consequent signal to noise reduction; and / or the modularity of the OADM, including the BiDi amplifier of various embodiments, with reflection reduction / cancellation may help enable evolution of silicon photonics technologies. Evolution of silicon photonics technologies may include the programmable OADM of various embodiments of the present disclosure, which may save costs and power consumption and may address drawbacks of present optical devices that may have a non-negligible insertion loss that limits their application in the field.

[0048] Figure 6 is a block diagram illustrating an OADM 601 in accordance with some embodiments of the present disclosure. OADM 601 may be tolerant to reflections (e.g., hinder reflections) and may be low loss. BiDi amplifier 603 includes a design that may hinder reflection effects (e.g., counteract or reduce reflection effects) by exploiting properties of three-port wavelength selective devices in combination with an appropriate wavelength mapping for downstream and upstream flows.

[0049] A 1:N splitter / combiner 605 and at least one tunable add-drop component 607a-607n may lend modularity and scalability of OADM 601, may provide a passthrough feature on an express (EXP) port (e.g., which may be needed for chain topology), and can provide a channel by channel wavelength programmability to change the configuration for available communication links on each pair of add-drop ports add 1, drop 1 - add n, drop n.

[0050] OADM 601 includes a cascade between the 1:N power splitter / combiner 605 and the N-l single channel tunable add-drop components 607a-607n to implement add / drop filter functionality. An unused power splitter / combiner port of splitter / combiner 605 may be used as an EXP port for deployment of OADM 601 in a chain architecture. BiDi amplifier 601 may reduce the losses of OADM 601 and includes an important role in counteracting reflections effects. Conventional BiDi amplifiers may be realized with optical amplifiers and with a direction-selective three-port devices, as discussed herein with respect to the BiDi amplifiers of Figures 2 and 4. Such BiDi amplifiers may have drawbacks discussed herein due to reflections effects that may arise in the communication network based on a single transmission optical fiber with bidirectional communication.

[0051] In some deployed communication network systems based on single optical fiber and bi-directional communications, wavelength mapping for downstream and upstream signals avoid the use of the same wavelength for the two propagation directions, upstream and downstream. Figure 7 is a block diagram illustrating a BiDi amplifier in accordance with some embodiments of the present disclosure. As shown in Figure 7, BiDi amplifier 601 includes two three-ports wavelength selective devices 701a, 701b, two OAs 205a, 205b, and two isolators 405a, 405b. Wavelength selection devices 701a, 701b can route each channel of the DWDM comb depending on the wavelength of the channel itself.

[0052] In various embodiments, a programmable OADM (e.g., OADM 601) is provided for a communication network having a bi-directional optical fiber. The OADM includes a BiDi amplifier (e.g., 603) including a first (e.g., 701a) and a second (e.g., 701b) three-port wavelength selection device respectively configured to route a downstream channel and / or an upstream channel from the bi-directional optical fiber based on a wavelength of the respective downstream channel or upstream channel. The OADM further includes a power splitter / combiner (e.g., 605) having (i) a common port connected to an output / input of the BiDi amplifier and (ii) a plurality of power splitter / combiner ports. The OADM further includes at least one tunable add-drop component (e.g., 607) comprising a common add / drop port connected to a respective one of the plurality of power splitter / combiner ports, a drop port configured to drop a defined wavelength from the downstream channel applied to the common add / drop port, and an add port configured to add to the common add / drop port an assigned wavelength from the upstream channel when the upstream channel is applied to the add port.

[0053] In some embodiments of the OADM, a respective one of the first and second wavelength selection devices is configured to route a downstream or an upstream channel of a dense wavelength division multiplexing comb based on the wavelength of the channel.

[0054] The type of three port wavelength selection device included can be based on the wavelength mapping selected for the network. For example, when upstream (up) and downstream (down) channels are in two separated communication bands, the three port wavelength selection device may be a band splitter (BS) as shown in Figure 8 illustrating optical signals and reflected signals travelling in BiDi amplifier 603 in accordance with some embodiments of the present disclosure. Band splitters 801a, 801b respectively create two different paths for wavelengths belonging to the same sub-bands addressing the reflections toward the respective output port 101a, 101b where the respective isolator 405b, 405a hinders them avoiding / lessening their back propagation.

[0055] In some embodiments of the OADM, when the downstream (down) channel and the upstream (up) channel are in separate communication bands, the respective first and second wavelength selection devices comprise a first band splitter (e.g., 801a) and a second band splitter (e.g., 801b), respectively. In some embodiments of the OADM, the first and second band splitters respectively include a communications port configured to connect to the bidirectional optical fiber, a first input / output port, and second input / output port.

[0056] As shown in Figure 8, the upstream (up) comb and the reflected downstream (R-D) comb come in by the Line West 101a port where band splitter 801a routes the upstream comb on input / output (I / O) port 803b toward OA205a; and band splitter 801a routes the R-D comb on I / O port 803c toward isolator 405b which hinders its propagation. The amplified upstream comb arrives at I / O port 807b of band splitter 801b where it is routed on communications port 707a and leaves BiDi amplifier 603 by Line East 101b port.

[0057] In the opposite direction, the downstream (down) comb and the reflected upstream (R- U) comb come into BiDi amplifier 603 from the Line East 101b port where band splitter 801b routes the downstream comb on port 807c toward OA 205b; and BiDi amplifier 603 routes the R-U comb on I / O port 807b toward the isolator 405a which hinders its propagation. The amplified downstream comb arrives at the I / O port 803c of band splitter 801a where it is routed on communications port 703a and leaves BiDi amplifier 603 by the Line West 101a port.

[0058] In some embodiments of the OADM, the first and second band splitters are respectively configured to create two paths for wavelengths belonging to a same sub-band comprising (i) a wavelength in the downstream channel or the upstream channel and (ii) a reflected wavelength from an optical reflection of a signal that travels in a direction opposite the wavelength in the downstream channel or the upstream channel.

[0059] In some embodiments of the OADM, the BiDi amplifier 603further includes a first optical amplifier 205a positioned between the first input / output ports of the first 801a and the second 801b band splitters and a second optical amplifier 205b positioned between the second input / output ports of the first 801a and the second 801b band splitters.

[0060] In some embodiments of the OADM, the BiDi amplifier 603 further includes a first isolator 405a positioned between the first input / output port of the first band splitter 801a and the first optical amplifier 205a, and a second isolator 405b positioned between the second input / output port of the second band splitter 801b and the second optical amplifier 205b.

[0061] In some embodiments of the OADM, the first isolator and the second isolator are configured to hinder propagation of the reflected wavelength.

[0062] In some embodiments of the OADM, the BiDi amplifier 603, is further configured to amplify the wavelength in the upstream channel with the first optical amplifier and route the amplified upstream wavelength to the communication port of the second band splitter.

[0063] In some embodiments of the OADM, the BiDi amplifier 603, is further configured to amplify the wavelength in the downstream channel with the second optical amplifier and route the amplified downstream wavelength to the communications port of the first band splitter.

[0064] In another embodiment, when the upstream (up) and the downstream (down) channels are interleaved (e.g., odd channels for downstream and even channels for upstream), the wavelength selection device can be an optical interleaver and reflected signals can be routed toward the output port of the isolator that hinders them concluding / lessening their back propagation. Figure 9 is a schematic diagram showing an example of an interleaver variant of BiDi amplifier 603.

[0065] In other words, in some embodiments of the OADM, when the downstream channel and the upstream channel are interleaved, the respective first and second wavelength selection devices include a first optical interleaver 901a having a first set of channels for downstream and a second optical interleaver 901b having a second set of channels for upstream, respectively.

[0066] In some embodiments of the OADM, the first 901a and second 901b optical interleavers respectively include a communication port configured to connect to the bidirectional optical fiber, a first input / output port, and second input / output port.

[0067] As shown in Figure 9, the upstream (up) comb is mapped on even channels of interleaver (IN) 901a and the reflected downstream (R-D) comb is mapped on odd channels of IN 901a. The upstream comb (even) and the R-D comb (odd) come in from the Line West 101a port and IN 901a routes the upstream comb on the even port 903b toward OA 205a; and BiDi amplifier 603 routes the R-D comb on the odd port 903c toward isolator 405b which hinders its propagation. The amplified upstream comb arrives at the even port 903c of IN 901b where it is routed on the communications port 707a and leaves the BiDi amplifier 603 by Line East 101b port.

[0068] In the opposite direction, the downstream (down) comb (odd) and the R-U comb (even) come into BiDi amplifier 603 by Line East 101b port where IN 901b routes the downstream comb on odd port 903d toward OA 205b; and BiDi amplifier 603 routes the R- U comb on even port 903c toward isolator 405a which hinders its propagation. The amplified downstream comb arrives at odd port 903a of IN 901a where it is routed on the communications port 703a and leaves BiDi amplifier 603 by Line West 101a port.

[0069] In some embodiments of the OADM, the BiDi amplifier 603further includes a first optical amplifier 205a positioned between the first input / output ports of the first 901a and the second 901b optical interleavers, respectively, and a second optical amplifier 205b positioned between the second input / output ports of the first and the second optical interleavers, respectively.

[0070] In some embodiments of the OADM, the BiDi amplifier 603further includes a first isolator 405a positioned between the first input / output port of the first optical interleaver and the first optical amplifier, and a second isolator 405b positioned between the second input / output port of the second optical interleaver and the second optical amplifier.

[0071] In some embodiments of the OADM, the first optical interleaver 901a is configured to route a wavelength of the upstream channel on the first input / output port of the first optical interleaver towards the first optical amplifier and a reflected downstream wavelength on the second input / output port of the first optical interleaver towards the second isolator.

[0072] In some embodiments of the OADM, the second optical interleaver 901b is configured to route a wavelength of the downstream channel on the second input / output port of the second optical interleaver towards the second optical amplifier and a reflected upstream wavelength on the first input / output port of the second optical interleaver towards the first isolator.

[0073] In some embodiments of the OADM, the BiDi amplifier 603, is further configured to amplify the wavelength in the upstream channel with the first optical amplifier 205a and route the amplified upstream wavelength to the communication port of the second optical interleaver 901b. The BiDi amplifier 603, in some embodiments of the OADM, is further configured to amplify the wavelength in the downstream channel with the second optical amplifier 205b and route the amplified downstream wavelength to the communications port of the first optical interleaver 901a.

[0074] In some embodiments of the OADM, the at least one tunable add-drop component 607 further includes a chain of a first tunable filter 1001a and a second tunable filter 1001b, as illustrated in Figure 10A, for example. A first tunable filter (TF) 1001a can select an added channel and the second TF 1001b can select a dropped channel. The first tunable filter 1001a, in some embodiments of the OADM, is configured to select the assigned wavelength from the upstream channel to add and the second tunable filter is configured to select the defined wavelength from the downstream channel to drop. First TF 1001 in the chain includes a three- port structure to allow the passthrough for wavelengths not filtered toward the second TF 1001b. In some embodiments of the OADM, the common add / drop port of the at least one tunable add-drop component 607 is configured to passthrough at least one wavelength not filtered toward the second tunable filter 1001b.

[0075] In another embodiment, T-A / D component 607 is implemented by parallelizing the two tunable filters 1001a, 1001b with a coupling device 1003, as illustrated in the example embodiment of Figure 10B. That is, in another embodiment of the OADM, the at least one tunable add-drop component 607 further includes a first tunable filter 1001a, a second tunable filter 1001b, and a coupling device 1003 positioned in parallel between the first tunable filter and the second tunable filter.

[0076] In some embodiments of the OADM, coupling device 1003 includes one of a band splitter and an optical interleaver. A band splitter may be used when a network wavelength plan assigns the channels in one direction at one of two sub-bands and the channels in the opposite direction are in the other sub-band. That is, in some embodiments of the OADM, when the coupling device 1003 comprises a band splitter for the upstream channel or the downstream channel, respectively, assigned by the communication network in a first direction in one of a first and a second sub-band and the downstream channel or the upstream channel, respectively, in a second direction that is opposite to the first direction in the other sub-band.

[0077] An optical interleaver may be used when the channels in the two opposite directions are interleaved. In some embodiments of the OADM, the coupling device 1003 includes an optical interleaver for interleaved upstream and downstream channels on the bi-directional optical fiber. In some embodiments, OADM 601 is implemented on a silicon photonic chip, except the optical amplifiers 205a, 205b. The optical amplifiers 205a, 205b, in some embodiments, are coupled to the silicon photonic chip through external connectors.

[0078] In some embodiments of the OADM, one of the plurality of the power splitter / combiner ports of the power splitter / combiner 605 includes an express port that is configured to passthrough the downstream and the upstream channels.

[0079] Some embodiments provide a bi-directional amplifier (e.g., 603) for a communication network having a bi-directional optical fiber. The bi-directional amplifier includes: a first three-port wavelength selection device (e.g., 701a); and a second three-port wavelength selection device (e.g., 701b). The first and the second three-port wavelength selection devices are respectively configured to route a downstream channel and / or an upstream channel from the bi-directional optical fiber based on a wavelength of the respective downstream channel or upstream channel.

[0080] In some embodiments of the bi-directional amplifier, a respective one of the first and second wavelength selection devices of the bi-directional amplifier is configured to route a downstream or an upstream channel of a dense wavelength division multiplexing comb based on the wavelength of the channel.

[0081] In some embodiments of the bi-directional amplifier, when the downstream channel and the upstream channel are in separate communication bands, the respective first and second wavelength selection devices comprise a first band splitter (e.g., 801a) and a second band splitter (e.g., 801b), respectively.

[0082] In some embodiments of the bi-directional amplifier, the first and second band splitters respectively include a communications port configured to connect to the bi-directional optical fiber, a first input / output port, and second input / output port.

[0083] In some embodiments of the bi-directional amplifier, the first and second band splitters are respectively configured to create two paths for wavelengths belonging to a same sub-band including (i) a wavelength in the downstream channel or the upstream channel and (ii) a reflected wavelength from an optical reflection of a signal that travels in a direction opposite the wavelength in the downstream channel or the upstream channel.

[0084] Some embodiments of the bi-directional amplifier further include a first optical amplifier (e.g., 205a) positioned between the first input / output ports of the first (e.g., 801a) and the second (e.g., 801b) band splitters and a second optical amplifier (e.g., 205b) positioned between the second input / output ports of the first (e.g., 801a) and the second (801b) band splitters.

[0085] Some embodiments of the bi-directional amplifier further include a first isolator (e.g., 405a) positioned between the first input / output port of the first band splitter (e.g., 801a) and the first optical amplifier (e.g., 205a), and a second isolator (e.g., 405b) positioned between the second input / output port of the second band splitter (e.g., 801b) and the second optical amplifier (e.g., 205b).

[0086] In some embodiments of the bi-directional amplifier, the first isolator and the second isolator are configured to hinder propagation of the reflected wavelength.

[0087] The bi-directional amplifier, in some embodiments, is further configured to amplify the wavelength in the upstream channel with the first optical amplifier and route the amplified upstream wavelength to the communication port of the second band splitter.

[0088] The bi-directional amplifier, in some embodiments, is further configured to amplify the wavelength in the downstream channel with the second optical amplifier and route the amplified downstream wavelength to the communications port of the first band splitter.

[0089] In some embodiments of the bi-directional amplifier, when the downstream channel and the upstream channel are interleaved, the respective first and second wavelength selection devices include a first optical interleaver (e.g., 901a) having a first set of channels for downstream and a second optical interleaver (e.g., 901b) having a second set of channels for upstream, respectively.

[0090] In some embodiments of the bi-directional amplifier, the first (e.g., 901a) and second (e.g., 901b) optical interleavers respectively include a communication port configured to connect to the bi-directional optical fiber, a first input / output port, and second input / output port.

[0091] The bi-directional amplifier, in some embodiments, further includes a first optical amplifier (e.g., 205a) positioned between the first input / output ports of the first (e.g., 901a) and the second (e.g., 901b) optical interleavers, respectively, and a second optical amplifier (e.g., 205b) positioned between the second input / output ports of the first and the second optical interleavers, respectively.

[0092] The bi-directional amplifier, of some embodiments, further includes a first isolator (e.g., 405a) positioned between the first input / output port of the first optical interleaver and the first optical amplifier, and a second isolator (e.g., 405b) positioned between the second input / output port of the second optical interleaver and the second optical amplifier. In some embodiments of the bi-directional amplifier, the first optical interleaver (e.g., 901a) is configured to route a wavelength of the upstream channel on the first input / output port of the first optical interleaver towards the first optical amplifier and a reflected downstream wavelength on the second input / output port of the first optical interleaver towards the second isolator.

[0093] In some embodiments of the bi-directional amplifier, the second optical interleaver (e.g., 901b) is configured to route a wavelength of the downstream channel on the second input / output port of the second optical interleaver towards the second optical amplifier and a reflected upstream wavelength on the first input / output port of the second optical interleaver towards the first isolator.

[0094] The bi-directional amplifier, in some embodiments, is further configured to amplify the wavelength in the upstream channel with the first optical amplifier (e.g., 205a) and route the amplified upstream wavelength to the communication port of the second optical interleaver (e.g., 901b).

[0095] The bi-directional amplifier, in some embodiments, is further configured to amplify the wavelength in the downstream channel with the second optical amplifier (e.g., 205b) and route the amplified downstream wavelength to the communications port of the first optical interleaver (e.g., 901a).

[0096] Further definitions and embodiments are discussed below.

[0097] In the above-description of various embodiments of the present disclosure, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of present inventive concepts. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which present inventive concepts belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0098] When an element is referred to as being "connected", "coupled", "responsive", or variants thereof to another element, it can be directly connected, coupled, or responsive to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected", "directly coupled", "directly responsive", or variants thereof to another element, there are no intervening elements present. Like numbers refer to like elements throughout. Furthermore, "coupled", "connected", "responsive", or variants thereof as used herein may include wirelessly coupled, connected, or responsive. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Well-known functions or constructions may not be described in detail for brevity and / or clarity. The term "and / or" (abbreviated “ / ”) includes any and all combinations of one or more of the associated listed items.

[0099] It will be understood that although the terms first, second, third, etc. may be used herein to describe various elements / operations, these elements / operations should not be limited by these terms. These terms are only used to distinguish one element / operation from another element / operation. Thus a first element / operation in some embodiments could be termed a second element / operation in other embodiments without departing from the teachings of present inventive concepts. The same reference numerals or the same reference designators denote the same or similar elements throughout the specification.

[0100] As used herein, the terms "comprise", "comprising", "comprises", "include", "including", "includes", "have", "has", "having", or variants thereof are open-ended, and include one or more stated features, integers, elements, steps, components or functions but does not preclude the presence or addition of one or more other features, integers, elements, steps, components, functions or groups thereof. Furthermore, as used herein, the common abbreviation "e.g.", which derives from the Latin phrase "exempli gratia," may be used to introduce or specify a general example or examples of a previously mentioned item, and is not intended to be limiting of such item. The common abbreviation "i.e.", which derives from the Latin phrase "id est," may be used to specify a particular item from a more general recitation.

[0101] Example embodiments are described herein with reference to block diagrams and / or flowchart illustrations of computer-implemented methods, apparatus (systems and / or devices) and / or computer program products. It is understood that a block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can be implemented by computer program instructions that are performed by one or more computer circuits. These computer program instructions may be provided to a processor circuit of a general purpose computer circuit, special purpose computer circuit, and / or other programmable data processing circuit to produce a machine, such that the instructions, which execute via the processor of the computer and / or other programmable data processing apparatus, transform and control transistors, values stored in memory locations, and other hardware components within such circuitry to implement the functions / acts specified in the block diagrams and / or flowchart block or blocks, and thereby create means (functionality) and / or structure for implementing the functions / acts specified in the block diagrams and / or flowchart block(s).

[0102] These computer program instructions may also be stored in a tangible computer- readable medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instructions which implement the functions / acts specified in the block diagrams and / or flowchart block or blocks. Accordingly, embodiments of present inventive concepts may be embodied in hardware and / or in software (including firmware, resident software, micro-code, etc.) that runs on a processor such as a digital signal processor, which may collectively be referred to as "circuitry," "a module" or variants thereof.

[0103] It should also be noted that in some alternate implementations, the functions / acts noted in the blocks may occur out of the order noted in the flowcharts. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality / acts involved. Moreover, the functionality of a given block of the flowcharts and / or block diagrams may be separated into multiple blocks and / or the functionality of two or more blocks of the flowcharts and / or block diagrams may be at least partially integrated. Finally, other blocks may be added / inserted between the blocks that are illustrated, and / or blocks / operations may be omitted without departing from the scope of inventive concepts. Moreover, although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

[0104] Many variations and modifications can be made to the embodiments without substantially departing from the principles of the present inventive concepts. All such variations and modifications are intended to be included herein within the scope of present inventive concepts. Accordingly, the above disclosed subject matter is to be considered illustrative, and not restrictive, and the examples of embodiments are intended to cover all such modifications, enhancements, and other embodiments, which fall within the spirit and scope of present inventive concepts. Thus, to the maximum extent allowed by law, the scope of present inventive concepts are to be determined by the broadest permissible interpretation of the present disclosure including the examples of embodiments and their equivalents, and shall not be restricted or limited by the foregoing detailed description.

Claims

CLAIMS:

1. A programmable optical add-drop multiplexer (601), OADM, for a communication network having a bi-directional optical fiber, the OADM comprising: a bi-directional amplifier (603) comprising a first (701a) and a second (701b) three- port wavelength selection device respectively configured to route a downstream channel and / or an upstream channel from the bi-directional optical fiber based on a wavelength of the respective downstream channel or upstream channel; a power splitter / combiner (605) having (i) a common port connected to an output / input of the bi-directional amplifier and (ii) a plurality of power splitter / combiner ports; and at least one tunable add-drop component (607) comprising a common add / drop port connected to a respective one of the plurality of power splitter / combiner ports, a drop port configured to drop a defined wavelength from the downstream channel applied to the common add / drop port, and an add port configured to add to the common add / drop port an assigned wavelength from the upstream channel when the upstream channel is applied to the add port.

2. The OADM of Claim 1, wherein a respective one of the first and second wavelength selection devices is configured to route a downstream or an upstream channel of a dense wavelength division multiplexing comb based on the wavelength of the channel.

3. The OADM of any one of Claims 1 to 2, wherein, when the downstream channel and the upstream channel are in separate communication bands, the respective first and second wavelength selection devices comprise a first band splitter (801a) and a second band splitter (801b), respectively.

4. The OADM of Claims 3, wherein the first and second band splitters respectively comprise a communications port configured to connect to the bi-directional optical fiber, a first input / output port, and second input / output port.

5. The OADM of any one of Claims 3 to 4, wherein the first and second band splitters are respectively configured to create two paths for wavelengths belonging to a samesub-band comprising (i) a wavelength in the downstream channel or the upstream channel and (ii) a reflected wavelength from an optical reflection of a signal that travels in a direction opposite the wavelength in the downstream channel or the upstream channel.

6. The OADM of any one of Claims 3 to 5, wherein the bi-directional amplifier (603) further comprises a first optical amplifier (205a) positioned between the first input / output ports of the first (801a) and the second (801b) band splitters and a second optical amplifier (205b) positioned between the second input / output ports of the first (801a) and the second (801b) band splitters.

7. The OADM of Claim 6, wherein the bi-directional amplifier (603) further comprises a first isolator (405a) positioned between the first input / output port of the first band splitter (801a) and the first optical amplifier (205a), and a second isolator (405b) positioned between the second input / output port of the second band splitter (801b) and the second optical amplifier (205b).

8. The OADM of any one of Claims 5 to 7, wherein the first isolator and the second isolator are configured to hinder propagation of the reflected wavelength.

9. The OADM of any one of Claims 5 to 8, wherein the bi-directional amplifier (603) is further configured to amplify the wavelength in the upstream channel with the first optical amplifier and route the amplified upstream wavelength to the communication port of the second band splitter.

10. The OADM of any one of Claims 5 to 9, wherein the bi-directional amplifier (603) is further configured to amplify the wavelength in the downstream channel with the second optical amplifier and route the amplified downstream wavelength to the communications port of the first band splitter.

11. The OADM of any one of Claims 1 to 2, wherein, when the downstream channel and the upstream channel are interleaved, the respective first and second wavelength selection devices comprise a first optical interleaver (901a) having a first set of channels fordownstream and a second optical interleaver (901b) having a second set of channels for upstream, respectively.

12. The OADM of Claim 11, wherein the first (901a) and second (901b) optical interleavers respectively comprise a communication port configured to connect to the bidirectional optical fiber, a first input / output port, and second input / output port.

13. The OADM of any one of Claims 10 to 12, wherein the bi-directional amplifier (603) further comprises a first optical amplifier (205a) positioned between the first input / output ports of the first (901a) and the second (901b) optical interleavers, respectively, and a second optical amplifier (205b) positioned between the second input / output ports of the first and the second optical interleavers, respectively.

14. The OADM of Claim 13, wherein the bi-directional amplifier (603) further comprises a first isolator (405a) positioned between the first input / output port of the first optical interleaver and the first optical amplifier, and a second isolator (405b) positioned between the second input / output port of the second optical interleaver and the second optical amplifier.

15. The OADM of Claim 14, wherein the first optical interleaver (901a) is configured to route a wavelength of the upstream channel on the first input / output port of the first optical interleaver towards the first optical amplifier and a reflected downstream wavelength on the second input / output port of the first optical interleaver towards the second isolator.

16. The OADM of any one of Claims 14 to 15, wherein the second optical interleaver (901b) is configured to route a wavelength of the downstream channel on the second input / output port of the second optical interleaver towards the second optical amplifier and a reflected upstream wavelength on the first input / output port of the second optical interleaver towards the first isolator.

17. The OADM of any one of Claims 13 to 16, wherein the bi-directional amplifier (603) is further configured to amplify the wavelength in the upstream channel with the firstoptical amplifier (205a) and route the amplified upstream wavelength to the communication port of the second optical interleaver (901b).

18. The OADM of any one of Claims 13 to 17, wherein the bi-directional amplifier (603) is further configured to amplify the wavelength in the downstream channel with the second optical amplifier (205b) and route the amplified downstream wavelength to the communications port of the first optical interleaver (901a).

19. The OADM of any one of Claims 1 to 18, wherein the at least one tunable adddrop component (607) further comprises a chain of a first tunable filter (1001a) and a second tunable filter (1001b).

20. The OADM of Claim 19, wherein the first tunable filter (1001a) is configured to select the assigned wavelength from the upstream channel to add and the second tunable filter is configured to select the defined wavelength from the downstream channel to drop.

21. The OADM of any one of Claims 19 to 20, wherein the common add / drop port of the at least one tunable add-drop component (607) is configured to passthrough at least one wavelength not filtered toward the second tunable filter (1001b).

22. The OADM of any one of Claims 1 to 18, wherein the at least one tunable adddrop component (607) further comprises a first tunable filter (1001a), a second tunable filter (1001b), and a coupling device (1003) positioned in parallel between the first tunable filter and the second tunable filter.

23. The OADM of Claim 22, wherein the coupling devices (1003) comprises one of a band splitter and an optical interleaver.

24. The OADM of Claim 23, wherein when the coupling device (1003) comprises a band splitter for the upstream channel or the downstream channel, respectively, assigned by the communication network in a first direction in one of a first and a second sub-band and the downstream channel or the upstream channel, respectively, in a second direction that is opposite to the first direction in the other sub-band.

25. The OADM of Claim 23, wherein the coupling device (1003) comprises an optical interleaver for interleaved upstream and downstream channels on the bi-directional optical fiber.

26. The OADM of any one of Claims 1 to 25, wherein the OADM (601) comprises a silicon photonic chip.

27. The OADM of Claim 26, wherein a first optical amplifier (205a) and a second optical amplifier (205b), respectively, are coupled to the silicon photonic chip through external connectors.

28. The OADM of any one of Claims 1 to 27, wherein one of the plurality of power splitter / combiner ports of the power splitter / combiner (605) comprises an express port that is configured to passthrough the downstream and the upstream channels.

29. A bi-directional amplifier (603) for a communication network having a bidirectional optical fiber, the bi-directional amplifier comprising: a first three-port wavelength selection device (701a); and a second three-port wavelength selection device (701b), wherein the first and the second three-port wavelength selection devices are respectively configured to route a downstream channel and / or an upstream channel from the bi-directional optical fiber based on a wavelength of the respective downstream channel or upstream channel.

30. The bi-directional amplifier (603) of Claim 29, wherein a respective one of the first and second wavelength selection devices is configured to route a downstream or an upstream channel of a dense wavelength division multiplexing comb based on the wavelength of the channel.

31. The bi-directional amplifier (603) of any one of Claims 29 to 30, wherein, when the downstream channel and the upstream channel are in separate communication bands, the respective first and second wavelength selection devices comprise a first band splitter (801a) and a second band splitter (801b), respectively.

32. The bi-directional amplifier (603) of Claim 31, wherein the first and second band splitters respectively comprise a communications port configured to connect to the bidirectional optical fiber, a first input / output port, and second input / output port.

33. The bi-directional amplifier (603) of any one of Claims 31 to 32, wherein the first and second band splitters are respectively configured to create two paths for wavelengths belonging to a same sub-band comprising (i) a wavelength in the downstream channel or the upstream channel and (ii) a reflected wavelength from an optical reflection of a signal that travels in a direction opposite the wavelength in the downstream channel or the upstream channel.

34. The bi-directional amplifier (603) of any one of Claims 31 to 33, wherein the bi-directional amplifier (603) further comprises a first optical amplifier (205a) positioned between the first input / output ports of the first (801a) and the second (801b) band splitters and a second optical amplifier (205b) positioned between the second input / output ports of the first (801a) and the second (801b) band splitters.

35. The bi-directional amplifier (603) of Claim 34, wherein the bi-directional amplifier (603) further comprises a first isolator (405a) positioned between the first input / output port of the first band splitter (801a) and the first optical amplifier (205a), and a second isolator (405b) positioned between the second input / output port of the second band splitter (801b) and the second optical amplifier (205b).

36. The bi-directional amplifier (603) of any one of Claims 33 to 35, wherein the first isolator and the second isolator are configured to hinder propagation of the reflected wavelength.

37. The bi-directional amplifier (603) of any one of Claims 33 to 36, wherein the bi-directional amplifier (603) is further configured to amplify the wavelength in the upstream channel with the first optical amplifier and route the amplified upstream wavelength to the communication port of the second band splitter.

38. The bi-directional amplifier (603) of any one of Claims 33 to 37, wherein the bi-directional amplifier (603) is further configured to amplify the wavelength in the downstream channel with the second optical amplifier and route the amplified downstream wavelength to the communications port of the first band splitter.

39. The bi-directional amplifier (603) of any one of Claims 29 to 30, wherein, when the downstream channel and the upstream channel are interleaved, the respective first and second wavelength selection devices comprise a first optical interleaver (901a) having a first set of channels for downstream and a second optical interleaver (901b) having a second set of channels for upstream, respectively.

40. The bi-directional amplifier (603) of Claim 39, wherein the first (901a) and second (901b) optical interleavers respectively comprise a communication port configured to connect to the bi-directional optical fiber, a first input / output port, and second input / output port.

41. The bi-directional amplifier (603) of any one of Claims 39 to 40, wherein the bi-directional amplifier (603) further comprises a first optical amplifier (205a) positioned between the first input / output ports of the first (901a) and the second (901b) optical interleavers, respectively, and a second optical amplifier (205b) positioned between the second input / output ports of the first and the second optical interleavers, respectively.

42. The bi-directional amplifier (603) of Claim 41, wherein the bi-directional amplifier (603) further comprises a first isolator (405a) positioned between the first input / output port of the first optical interleaver and the first optical amplifier, and a second isolator (405b) positioned between the second input / output port of the second optical interleaver and the second optical amplifier.

43. The bi-directional amplifier (603) of Claim 42, wherein the first optical interleaver (901a) is configured to route a wavelength of the upstream channel on the first input / output port of the first optical interleaver towards the first optical amplifier and a reflected downstream wavelength on the second input / output port of the first optical interleaver towards the second isolator.

44. The bi-directional amplifier (603) of any one of Claims 42 to 43, wherein the second optical interleaver (901b) is configured to route a wavelength of the downstream channel on the second input / output port of the second optical interleaver towards the second optical amplifier and a reflected upstream wavelength on the first input / output port of the second optical interleaver towards the first isolator.

45. The bi-directional amplifier (603) of any one of Claims 42 to 44, wherein the bi-directional amplifier (603) is further configured to amplify the wavelength in the upstream channel with the first optical amplifier (205a) and route the amplified upstream wavelength to the communication port of the second optical interleaver (901b).

46. The bi-directional amplifier (603) of any one of Claims 42 to 45, wherein the bi-directional amplifier (603) is further configured to amplify the wavelength in the downstream channel with the second optical amplifier (205b) and route the amplified downstream wavelength to the communications port of the first optical interleaver (901a).

Images