Optical filter latency equalization

Abstract

A padding unit is provided that includes one or more fiber paddings, each for a respective one of one or more pairs of bonded channels in an optical device, where in each pair of bonded channels, one channel in the pair of bonded channels is used as an upstream channel and the other channel in the pair of bonded channels is used as a downstream channel, each fiber padding includes a fiber padding length configured to offset at least a portion of a latency imbalance in each pair of bonded channels, the latency imbalance being a difference in latency between the respective upstream and downstream channels caused by a difference in multiplexing or demultiplexing path length of the respective upstream and downstream channels.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to optical communications, and in particular to a padding unit, an optical device, and a method for manufacturing the padding unit. [Background technology]

[0002] In general, all terms used herein should be interpreted according to the ordinary meaning of the term in the relevant technical field, unless a different meaning is clearly given and / or implied from the context in which the term is used. All references to a / an / the element, apparatus, component, means, step, etc. should be openly interpreted as referring to at least one instance of that element, apparatus, component, means, step, etc., unless expressly stated otherwise. The steps of the methods disclosed herein need not be performed in the strict order disclosed, unless expressly described as a step following or preceding another step, and / or where it is implicit that a step must follow or precede another step. Any feature of the embodiments disclosed herein may be applied to any other embodiment, whenever appropriate. Similarly, any advantage of any of the embodiments may be applied to any other embodiment, and vice versa. Other objectives, features, and advantages of the enclosed embodiments will become apparent from the following description.

[0003] Latency imbalance is a key parameter in today's fifth generation (5G) networks, as it impacts 5G performance. The maximum tolerance for proper operation is less than about + / - 65ns. Along the chain of communication paths, i.e. along the link between baseband and radio for the Radio Access Network (RAN), there are several items that can affect the latency balance for 5G networks. These include active devices such as Small Form-factor Pluggable (SFP) transceivers, Fronthaul (FH) units (which can be both active and passive, or only passive, such as optical multiplexers / demultiplexers), where latency imbalance is already under control, and where duplex fiber is also used.

[0004] However, currently, there are still some challenges. Specifically, latency imbalance in optical filters does not appear to be under control. Currently, optical filter manufacturing is optimized for cost-performance flexibility and availability. Thin film filters are offered as a solution for situations where low channel count, low cost, and low optical loss are required. Thin film filter modules include cascaded 3-port single filters spliced ​​together. For example, Figure 1 is an overview of a thin film filter module, e.g., a dense wavelength division multiplexing (DWDM) fronthaul optical thin film filter containing multiple channels.

[0005] Thin film filter modules having fewer or more ports all contain a three-port single filter spliced ​​together similar to that shown in FIG.

[0006] Each connection between one single filter and another is approximately 0.5-0.7 m. 1 m of single mode fiber may be assumed to have a delay of 5 ns. In a single fiber configuration, the upstream and downstream channels are typically spaced close to each other, e.g., wavelengths adjacent to each other, to reduce or minimize the difference in delay across the optical path. This difference in delay due to propagation in these channels has a negligible contribution over a fronthaul distance of approximately 15 km.

[0007] Figure 2 shows the internal structure of the thin film filter module. Depending on the materials available at different suppliers, the internal scheme of the thin film filter module may differ.

[0008] Returning to the scheme shown in Figure 1, in this example, channel 37 (CH37) and channel 36 (CH36), which form a bonded channel pair, are separated by about 5.5 to 7.7 m of fiber, meaning that there is a delay of about 27.5 ns (= 5.5 x 5 ns) to 38.5 ns (= 7.7 x 5 ns). The delay symmetry is therefore broken only by a single filter, which results in a high value of latency imbalance. Cascading another filter in this configuration means that the tolerance margin of 65 ns may be exceeded. The latency imbalance between the upstream and downstream directions can cause serious impacts on 5G operation. Summary of the Invention

[0009] Some aspects of the present disclosure and embodiments of those aspects may provide solutions to these or other problems. According to some embodiments, a solution is proposed to introduce latency padding inside the optical filter module to reduce (or equalize) the latency imbalance between the upstream and downstream channels. The latency padding may be achieved by introducing a stretch of fiber with a certain length to provide the same delay as the delay in the combined channels.

[0010] Various embodiments are proposed herein that address one or more of the problems disclosed herein.

[0011] According to some embodiments described herein, a padding unit is provided that includes one or more fiber paddings, each of which is for a respective one of one or more pairs of bonded channels in an optical device. In each pair of bonded channels, one channel in the pair of bonded channels is used as an upstream channel, and the other channel in the pair of bonded channels is used as a downstream channel. Each fiber padding includes a fiber padding length configured to offset at least a portion of a latency imbalance in each pair of bonded channels, the latency imbalance being a difference in latency between the respective upstream and downstream channels caused by a difference in multiplexing or demultiplexing path length of the respective upstream and downstream channels.

[0012] In some embodiments, the padding unit may include a plurality of fiber paddings. In these embodiments, each of the plurality of fiber paddings may be for a respective one of at least a subset of the plurality of pairs of bonded channels in the device. The fiber padding length in each of the plurality of fiber paddings may be configured to offset at least a portion of the latency imbalance in each pair of bonded channels such that differences in latency imbalance across the pairs of bonded channels are reduced. Alternatively, the fiber padding length in each of the plurality of fiber paddings may be configured to offset at least a portion of the latency in at least one channel of each pair of bonded channels such that the latency across all channels in the plurality of pairs of bonded channels is equalized to a common value.

[0013] In some embodiments, a padding length of fiber of each fiber padding may be disposed at the outlet of a respective pair of coupled channels.

[0014] In some embodiments, the padding length of each fiber padding may be determined based on the nominal splice length of the fibers in each pair of bonded channels.

[0015] In some embodiments, the padding length of each fiber padding may be determined based on a measured difference in path length of the upstream and downstream channels in each pair of bonded channels following splicing of the fibers in each pair of bonded channels.

[0016] In some embodiments, the padding length of each fiber padding may be determined based on measured delays in the upstream and downstream channels of each pair of bonded channels, the delays being caused by the path lengths of the respective upstream and downstream channels.

[0017] According to some embodiments, an optical device is provided that includes one or more pairs of bonded channels, where in each pair of bonded channels, one of the channels is used as an upstream channel and the other of the channel is used as a downstream channel, and a padding unit as described herein for at least one of the one or more pairs of bonded channels.

[0018] According to some embodiments, a method for manufacturing a padding unit is provided. The padding unit includes one or more fiber paddings, each of the one or more fiber paddings for a respective one of one or more pairs of bonded channels in an optical device. In each pair of bonded channels, one channel in the pair of bonded channels is used as an upstream channel and the other channel in the pair of bonded channels is used as a downstream channel. The method includes determining a padding length of each of the one or more fiber paddings, the padding length offsetting at least a portion of a latency imbalance in each pair of bonded channels, the latency imbalance being a difference in latency between the respective upstream and downstream channels caused by a difference in multiplexing or demultiplexing path length of the respective upstream and downstream channels, and forming the one or more fiber paddings based on the one or more determined padding lengths.

[0019] In some embodiments, the padding unit may include a plurality of fiber paddings. In these embodiments, each fiber padding may be for a respective one of at least a subset of the plurality of pairs of bonded channels in the optical device. The fiber padding length in each of the plurality of fiber paddings may be configured to offset at least a portion of the latency imbalance in each pair of bonded channels such that differences in latency imbalance across the pairs of bonded channels are reduced. Alternatively, the fiber padding length in each of the plurality of fiber paddings is configured to offset at least a portion of the latency in at least one channel of each pair of bonded channels such that the latency across all channels in the plurality of pairs of bonded channels is equalized to a common value.

[0020] In some embodiments, determining the padding length of each fiber padding may be based on one of: a nominal splice length of the fiber in each pair of bonded channels; a measured difference in path lengths of the upstream and downstream channels in each pair of bonded channels following splice connection of the fiber in each pair of bonded channels; and a measured delay in the upstream and downstream channels of each pair of bonded channels, where the delay is caused by the path lengths of the respective upstream and downstream channels.

[0021] Some embodiments may provide one or more of the following technical advantage(s): Some embodiments allow latency imbalance in optical filter cassettes / boxes, more specifically, latency imbalance in optical multiplexers / demultiplexers, to be reduced or minimized by introducing appropriate fiber padding. The solution proposed herein is easy to implement since the padding can be incorporated or built into the current optical filters and no external components / devices are required to achieve the latency equalization effect, and there is no (or only minimal) change to the current manufacturing process of the optical filters to include the latency padding according to the proposed solution. Furthermore, the proposed solution is low-cost since the extra cost of fiber material for manufacturing the padding is negligible compared to the cost of manufacturing other components in the optical filter. Furthermore, the proposed solution does not involve any change to the form factor of the optical filter and therefore does not involve any change to the related installation guidelines.

[0022] For a better understanding of examples of the present disclosure and to show more clearly how these may be carried out, reference will now be made, by way of example only, to the following drawings in which: [Brief description of the drawings]

[0023] [Figure 1] FIG. 9 is a schematic diagram showing the internal scheme of the service optical thin film filter module. [Diagram 2] 1 is a photograph of the internal structure of a thin film filter module. [Diagram 3] FIG. 1 is a schematic diagram showing a 9-service optical thin film filter module including latency padding. [Figure 4] FIG. 1 illustrates a schematic diagram of a wireless network according to some embodiments. [Diagram 5] 1 is a flowchart illustrating a method according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings, in which: However, other embodiments are included within the scope of the subject matter disclosed herein, and the disclosed subject matter should not be construed as being limited to only the embodiments described herein, but rather, these embodiments are provided as examples to convey the scope of the subject matter to those skilled in the art.

[0025] To illustrate some of the embodiments of the present disclosure as an example, FIG. 3 shows a diagram of a nine-service optical thin-film module including latency padding according to the proposed solution.

[0026] The configuration shown in Figure 3 corresponds to the configuration shown in Figure 1, with the difference that the configuration in Figure 3 further includes latency padding for channels 36 and 37. As described above with reference to Figure 1, channel 36 (CH36) and channel (CH37), a pair of combined channels in which channel 36 is used or arranged as an upstream channel and channel 37 is used or arranged as a downstream channel, or channel 36 is used or arranged as a downstream channel and channel 37 is used or arranged as an upstream channel, are separated by about 5.5 to 7.7 m of fiber. Thus, channel 36 has an additional delay of about 27.5 to 38.5 ns relative to channel 37.

[0027] To reduce the latency imbalance between channels 36 and 37, in this example, an appropriate length of fiber can be introduced at the outlet of the bonded channel. As shown in FIG. 3, a length of fiber is added to channel 37 so that instead of 0.5 m, the (padded) fiber in the channel is 5.5 m. Thus, the additional delay of about 27.5 to 38.5 ns in channel 36 matches the delay in channel 37. The same approach can be applied to all paired channels in the filter module to include the respective appropriate length of fiber for the bonded channel to reduce the respective latency imbalance.

[0028] The length of the fiber for latency padding may be determined according to one of the following: (1) Determine the fiber length based on the assumption that the splice length of the fibers in the coupled channels is the nominal splice length (or at least close to the nominal splice length). (2) Measure the actual lengths of the fiber in the combined channels after splicing (because splices may have to be repeated during the manufacturing process) and determine the length of fiber needed to compensate for the difference in optical path length based on the measured lengths. (3) Measure the actual delay in the upstream and downstream channels (e.g., using appropriate instrumentation) and determine, based on the measured delay, the length of fiber required to compensate for the difference in delay caused by the difference in optical path length.

[0029] In terms of implementation, the complexity increases from technique (1) to (3). However, the accuracy of the compensation (of latency imbalance) also increases with the complexity. Thus, the technique selected to determine the padding length may be selected depending on factors such as cost considerations and the availability of measurement equipment (to measure length or to measure delay).

[0030] According to some embodiments of the present disclosure, a padding unit is provided that includes one or more fiber paddings.

[0031] In one embodiment, the padding unit may include single fiber padding, and the fiber padding may be for a particular pair of bonded channels in an optical device, such as an optical multiplexer device or an optical demultiplexer device. The bonded channels include one channel used (or arranged) as an upstream channel and another channel used (or arranged) as a downstream channel. The fiber padding in this embodiment may include a padding length of fiber (that may be added / attached to one of the channels) to offset at least a portion of the latency imbalance in the pair of bonded channels. The latency imbalance refers to the difference in latency (or delay) between the upstream and downstream channels (e.g., the difference in the time it takes a signal to traverse the upstream and downstream channels), which is caused by the difference in the multiplexing / demultiplexing path lengths of the upstream and downstream channels. In some embodiments, the padding length may be determined such that when fiber padding is added to the channels in a bonded channel, the fiber length equalizes the latency between the two channels in the bonded channel pair (or at least reduces the latency difference, preferably minimizes the latency difference to a negligible degree).

[0032] In this embodiment, a padding length of fiber of each fiber padding may be configured to be disposed at the outlet of a respective pair of coupled channels.

[0033] The padding length of the fiber padding may be determined (or configured) based on the nominal splice length of the fiber in the bonded channel pair, or based on a measured difference in the path lengths of the upstream and downstream channels in the bonded channel pair following splice connection of the fiber in the bonded channel pair, or based on a measured delay in the upstream and downstream channels of the bonded channel pair, where the delay is caused (at least in part) by the path lengths of the upstream and downstream channels.

[0034] In another embodiment, the padding unit may include a plurality of fiber paddings. In this embodiment, each of the plurality of fiber paddings may be for a respective one of at least a subset of a plurality of pairs of bonded channels in the optical multiplexer or demultiplexer device. For example, in some embodiments, only some pairs of bonded channels (out of all the bonded channels) are provided with fiber padding (each). As in the above-described embodiment, each pair of bonded channels includes one channel used or arranged as an upstream channel and another channel used or arranged as a downstream channel.

[0035] Each fiber padding in this embodiment may include an individual padding length of fiber (that may be added / attached to one of the channels in each pair of bonded channels) to offset at least a portion of the latency imbalance in each pair of bonded channels. As mentioned above, latency imbalance refers to the difference in latency (or delay) between the upstream and downstream channels in each pair of bonded channels, which is caused by the difference in multiplexing / demultiplexing path length of the upstream and downstream channels in each pair of bonded channels.

[0036] More specifically, in this embodiment, the fiber padding length in each of the multiple fiber paddings may be configured to offset at least a portion of the latency imbalance in each pair of bonded channels such that the difference in latency imbalance across the pair of bonded channels is reduced. In some embodiments, the latency imbalance across all pairs of bonded channels in an optical multiplexer or demultiplexer device may be equalized through the use of multiple fiber paddings. The fiber padding length of each fiber padding may be configured to be placed, for example, at the outlet of each pair of bonded channels.

[0037] Alternatively, in this embodiment, the fiber padding length in each of the multiple fiber paddings may be configured to offset at least a portion of the latency in at least one channel of a respective pair of bonded channels such that the latency across all channels in the multiple pairs of bonded channels is equalized to a common value.

[0038] The padding length of each fiber padding may be determined based on the nominal splice length of the fiber in each pair of bonded channels, or based on a measured difference in the path lengths of the upstream and downstream channels in each pair of bonded channels following a splice connection of the fiber in each pair of bonded channels, or based on a measured delay in the upstream and downstream channels of each pair of bonded channels, where the delay is caused by the path lengths of the respective upstream and downstream channels.

[0039] According to some embodiments of the present disclosure, an optical device, for example an optical multiplexer device or an optical demultiplexer device, is provided. The device includes one or more pairs of bonded channels, and in each pair of bonded channels (or among them), one of the channels is used (or arranged) as an upstream channel and the other of the channels is used (or arranged) as a downstream channel. The device further includes a padding unit as described herein, for example according to one of the above-mentioned embodiments. For example, the device may include a padding unit comprising a plurality of fiber paddings for some of the pairs of bonded channels in the device.

[0040] According to some embodiments of the present invention there is provided a network node, comprising an optical device, for example an optical multiplexer or demultiplexer device, including a padding unit as described above. The network node may be a fronthaul network node.

[0041] Although the subject matter described herein may be implemented in any suitable type of system using any suitable components, the embodiments disclosed herein are described with respect to a wireless network, such as the exemplary wireless network shown in FIG. 4. For simplicity, the wireless network of FIG. 4 shows only network 406, network nodes 460 and 460b, and WD 410, 410b, and 410c. In practice, the wireless network may further include any additional elements suitable for supporting communication between wireless devices, or between a wireless device and another communication device, such as a landline telephone, a service provider, or any other network node or end device. Of the components shown, network node 460 and wireless device (WD) 410 are shown with additional details. A wireless network may provide communication and other types of services to one or more wireless devices to facilitate the wireless device's access to the wireless network and / or use of services provided by or through the wireless network.

[0042] A wireless network may comprise and / or interface with any type of communication, telecommunication, data, cellular, and / or radio network, or other similar type of system. In some embodiments, a wireless network may be configured to operate according to a particular standard or other type of predefined rules or procedures. Thus, particular embodiments of a wireless network may implement communication standards such as Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE), and / or other suitable 2G, 3G, 4G, or 5G standards, wireless local area network (WLAN) standards such as the IEEE 802.11 standard, and / or any other suitable wireless communication standards such as Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, and / or ZigBee standards.

[0043] The network 406 may include one or more backhaul networks, core networks, IP networks, public switched telephone networks (PSTN), packet data networks, optical networks, wide area networks (WANs), local area networks (LANs), wireless local area networks (WLANs), wired networks, wireless networks, metropolitan area networks, and other networks that enable communication between devices.

[0044] Network node 460 and WD 410 comprise various components, which are described in more detail below. These components cooperate to provide the functionality of a network node and / or a wireless device, such as providing wireless connectivity in a wireless network. In different embodiments, a wireless network may comprise any number of wired or wireless networks, network nodes, base stations, controllers, wireless devices, relay stations, and / or any other components or systems that may facilitate or be involved in the communication of data and / or signals, whether via wired or wireless connections.

[0045] As shown, the wireless device 410 includes an antenna 411 , an interface 414 , processing circuitry 420 , device-readable medium 430 , user interface equipment 432 , auxiliary equipment 434 , a power source 436 , and power circuitry 437 .

[0046] As shown, the interface 414 comprises a radio front-end circuit 412 and an antenna 411. The radio front-end circuit 412 comprises one or more filters 418 and amplifiers 416. The radio front-end circuit 414 is coupled to the antenna 411 and the processing circuit 420 and configured to condition signals communicated between the antenna 411 and the processing circuit 420. As shown, the processing circuit 420 includes one or more of an RF transceiver circuit 422, a baseband processing circuit 424, and an application processing circuit 426. As used herein, a "network node" refers to equipment that can, is configured to, is arranged to, and / or is operable to communicate directly or indirectly with wireless devices and / or other network nodes, or equipment in a wireless network that enables and / or provides wireless access to wireless devices and / or performs other functions (e.g., management) of the wireless network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., wireless access points), base stations (BSs) (e.g., wireless base stations, Node Bs, evolved Node Bs (eNBs) and new wireless Node Bs (gNBs)). Base stations may be categorized based on the amount of coverage they provide (or in other words, their transmit power level), and therefore may also be referred to as femto, pico, micro, or macro base stations. A base station may be a relay node or a relay donor node, which controls a relay. A network node may also include one or more (or all) parts of a distributed radio base station, such as a centralized digital unit and / or a remote radio unit (RRU), which may be referred to as a remote radio head (RRH). Such remote radio units may or may not be integrated with an antenna as an antenna-integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).Still further examples of network nodes include MSR equipment such as a Multi-Standard Radio (MSR) BS, a network controller such as a Radio Network Controller (RNC) or Base Station Controller (BSC), a base transceiver station (BTS), a transmission point, a transmitting node, a multi-cell / multicast coordination entity (MCE), a core network node (e.g., a mobile switching center, a mobility management entity), an operation and maintenance node, an operation support system node, a self-organizing network node, a positioning node (e.g., an evolved serving mobile location center), and / or a drive test minimization. As another example, a network node may be a virtual network node, which will be described in more detail below. However, more generally, a network node may represent any suitable device (or group of devices) capable of, configured, arranged, and / or operable to enable and / or provide wireless devices with access to a wireless network, or to provide some service to wireless devices that have accessed the wireless network.

[0047] In FIG. 4, network node 460 includes processing circuitry 470, device readable medium 480, interface 490, auxiliary equipment 484, power source 486, power circuitry 487, and antenna 462. Although network node 460 shown in the example wireless network of FIG. 4 may represent a device including the illustrated combination of hardware components, other embodiments may comprise network nodes having different combinations of components. It should be understood that a network node comprises any suitable combination of hardware and / or software necessary to perform the tasks, features, functions, and methods disclosed herein. Furthermore, although the components of network node 460 are shown as a single box located within a larger box or as a single box nested within multiple boxes, in reality the network node may comprise multiple different physical components that make up a single depicted component (e.g., device readable medium 480 may comprise multiple separate hard drives as well as multiple RAM modules).

[0048] Similarly, the network node 460 may be assembled from multiple physically separate components (e.g., a Node B component and an RNC component, or a BTS component and a BSC component, etc.), each of which may have their own respective components. In some scenarios in which the network node 460 comprises multiple separate components (e.g., a BTS component and a BSC component), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control several Node Bs. In such scenarios, each unique Node B and RNC pair may be considered as a single separate network node in some cases. In some embodiments, the network node 460 may be configured to support several radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate device-readable media 480 for different RATs) and some components may be reused (e.g., the same antenna 462 may be shared by the RATs). Network node 460 may also include multiple sets of the various components shown for different wireless technologies, such as, for example, GSM, WCDMA, LTE, NR, WiFi, or Bluetooth wireless technologies, integrated into network node 460. These wireless technologies may be integrated in the same or different chips or sets of chips and other components within network node 460.

[0049] In some embodiments, the processing circuitry 470 may include one or more of radio frequency (RF) transceiver circuitry 472 and baseband processing circuitry 474.

[0050] The interface 490 is used for wired or wireless communication of signaling and / or data between the network node 460, the network 406, and / or the WD 410. As shown, the interface 490 comprises a port / terminal 494 that transmits and receives data to and from the network 406, for example, through a wired connection. In certain embodiments, the port / terminal 494 may comprise an optical multiplexer device and / or an optical demultiplexer device as described herein. The interface 490 also includes a radio front-end circuit 492 that is coupled to the antenna 462 or may be part of the antenna 462 in certain embodiments. The radio front-end circuit 492 comprises a filter 498 and an amplifier 496. The radio front-end circuit 492 may be connected to the antenna 462 and the processing circuit 470. The radio front-end circuit may be configured to condition signals communicated between the antenna 462 and the processing circuit 470.

[0051] According to some embodiments of the present disclosure, a method for manufacturing a padding unit is provided, which will be described in more detail below with reference to Fig. 5. Also, according to some embodiments of the present disclosure, a method for manufacturing an optical multiplexer device or an optical demultiplexer device is provided, which will also be described in more detail below.

[0052] 5 illustrates a method for manufacturing a padding unit comprising one or more fiber paddings, each for a respective one of one or more pairs of bonded channels in an optical multiplexer or demultiplexer device, in which, in each pair of bonded channels, one channel in the pair of bonded channels is used as an upstream channel and the other channel in the pair of bonded channels is used as a downstream channel, according to a particular embodiment.

[0053] The method begins with step 502 of determining a padding length for each of one or more fiber paddings. The padding length offsets at least a portion of a latency imbalance in each pair of bonded channels, the latency imbalance being the difference in latency between the respective upstream and downstream channels caused by differences in the multiplexing or demultiplexing path lengths of the respective upstream and downstream channels.

[0054] In some embodiments, the padding unit may comprise a plurality of fiber paddings, each fiber padding for a respective one of at least a subset of the plurality of pairs of bonded channels in the optical multiplexer or demultiplexer device. In these embodiments, the fiber padding length in each of the plurality of fiber paddings may be configured to offset at least a portion of the latency imbalance in each pair of bonded channels such that the difference in latency imbalance across the pairs of bonded channels is reduced (preferably minimized). Alternatively, in these embodiments, the fiber padding length in each of the plurality of fiber paddings may be configured to offset at least a portion of the latency in at least one channel of each pair of bonded channels such that the latency across all channels in the plurality of pairs of bonded channels is equalized to a common value.

[0055] In some embodiments, determining the padding length of each fiber padding in step 502 may be based on one of: a nominal splice length of the fiber in each pair of bonded channels, a measured difference in path lengths of the upstream and downstream channels in each pair of bonded channels following splice connection of the fiber in each pair of bonded channels, and a measured delay in the upstream and downstream channels of each pair of bonded channels, where the delay is caused by the path lengths of the respective upstream and downstream channels.

[0056] The method then proceeds to step 504 of forming one or more fiber paddings based on the one or more determined padding lengths.

[0057] Although not shown in FIG. 5, it will be appreciated that according to some embodiments, a method for manufacturing an optical device (e.g., an optical multiplexer device or an optical demultiplexer device) is also provided. The optical device, such as an optical multiplexer device or an optical demultiplexer device, comprises one or more pairs of bonded channels and a padding unit as described herein. In these embodiments, the method may include, in addition to steps 502 and 504 of FIG. 5, the steps of forming one or more pairs of bonded channels, each pair of bonded channels including a channel to be used as an upstream channel and a channel to be used as a downstream channel, and attaching (or connecting) each of the one or more fiber paddings to a respective one of the one or more pairs of bonded channels. In one embodiment, a method for manufacturing an optical device (e.g., an optical multiplexer device or an optical demultiplexer device) includes providing one or more pairs of coupled channels as described herein and attaching (or connecting) each of one or more fiber paddings as described herein to a respective one of the one or more pairs of coupled channels.

Claims

1. An optical device, comprising: one or more pairs of bonded channels, where in each pair of bonded channels, one of the channels is used as an upstream channel and the other of the channels is used as a downstream channel; and a padding unit for at least one of the one or more pairs of bonded channels; The padding unit is one or more fiber paddings, each of the one or more fiber paddings for a respective one of one or more pairs of coupled channels in the optical device; an optical device, wherein each fiber padding includes a fiber padding length configured to offset at least a portion of a latency imbalance in the respective pair of bonded channels, the latency imbalance being a difference in latency between the respective upstream and downstream channels caused by a difference in multiplexing or demultiplexing path length of the respective upstream and downstream channels.

2. the padding unit comprises a plurality of fiber paddings, each of the plurality of fiber paddings for a respective one of at least a subset of the plurality of pairs of coupled channels in the optical device; 2. The optical device of claim 1, wherein the padding length of fiber in each of the plurality of fiber paddings is configured to offset at least a portion of the latency imbalance in the respective pair of bonded channels such that the difference in latency imbalance across the pair of bonded channels is reduced.

3. the padding unit comprises a plurality of fiber paddings, each of the plurality of fiber paddings for a respective one of at least a subset of the plurality of pairs of coupled channels in the optical device; 2. The optical device of claim 1, wherein a fiber padding length in each of the plurality of fiber paddings is configured to offset at least a portion of a latency in at least one channel of the respective pair of bonded channels such that latency across all channels in the plurality of pairs of bonded channels is equalized to a common value.

4. The optical device of claim 1 , wherein the padding length of fiber of each fiber padding is disposed at the outlet of the respective pair of coupled channels.

5. The optical device of claim 1 , wherein the padding length of each fiber padding is determined based on a nominal splice length of the fiber in the respective pair of bonded channels.

6. 2. The optical device of claim 1, wherein the padding length of each fiber padding is determined based on a measured difference in path lengths of the upstream and downstream channels in the respective pair of bonded channels following fiber splicing in the respective pair of bonded channels.

7. 2. The optical device of claim 1, wherein the padding length of each fiber padding is determined based on a measured delay in the upstream and downstream channels of the respective pair of bonded channels, the delay caused by the path length of the respective upstream and downstream channels.

8. The optical device of claim 1 , wherein the optical device is an optical filter module.

9. The optical device of claim 1 , wherein the optical device is an optical multiplexer device or an optical demultiplexer device.

10. A network node comprising an optical device according to any one of claims 1 to 9.

11. The network node of claim 10 , wherein the network node is a fronthaul network node.

12. a padding unit comprising one or more fiber paddings, each of the one or more fiber paddings for a respective one of one or more pairs of bonded channels in an optical device, wherein in each pair of bonded channels, one channel in the pair of bonded channels is used as an upstream channel and the other channel in the pair of bonded channels is used as a downstream channel; a padding unit, each fiber padding including a fiber padding length configured to offset at least a portion of a latency imbalance in the respective pair of bonded channels, the latency imbalance being a difference in latency between the respective upstream and downstream channels caused by a difference in multiplexing or demultiplexing path length of the respective upstream and downstream channels;

13. the padding unit comprises a plurality of fiber paddings, each of the plurality of fiber paddings for a respective one of at least a subset of the plurality of pairs of coupled channels in the optical device; 13. The padding unit of claim 12, wherein the padding length of fiber in each of the plurality of fiber paddings is configured to offset at least a portion of the latency imbalance in the respective pair of bonded channels such that the difference in latency imbalance across the pair of bonded channels is reduced.

14. the padding unit comprises a plurality of fiber paddings, each of the plurality of fiber paddings for a respective one of at least a subset of the plurality of pairs of coupled channels in the optical device; 13. The padding unit of claim 12, wherein a fiber padding length in each of the plurality of fiber paddings is configured to offset at least a portion of a latency in at least one channel of the respective pair of bonded channels such that latency across all channels in the plurality of pairs of bonded channels is equalized to a common value.

15. 13. The padding unit of claim 12, wherein the padding lengths of fiber of each fiber padding are for placement at the outlets of the respective pairs of coupled channels.

16. The padding unit of claim 12 , wherein the padding length of each fiber padding is determined based on a nominal splice length of the fibers in the respective pair of bonded channels.

17. 13. The padding unit of claim 12, wherein the padding length of each fiber padding is determined based on a measured difference in path lengths of the upstream and downstream channels in the respective pair of bonded channels following fiber splicing in the respective pair of bonded channels.

18. 13. The padding unit of claim 12, wherein the padding length of each fiber padding is determined based on a measured delay in the upstream and downstream channels of the respective pair of bonded channels, the delay caused by the path length of the respective upstream and downstream channels.

19. 1. A method for manufacturing a padding unit, the padding unit comprising one or more fiber paddings, each of the one or more fiber paddings for a respective one of one or more pairs of bonded channels in an optical device, wherein in each pair of bonded channels, one channel in the pair of bonded channels is used as an upstream channel and the other channel in the pair of bonded channels is used as a downstream channel, the method comprising: determining (502) a padding length for each of the one or more fiber paddings, the padding length offsetting at least a portion of a latency imbalance in the respective pair of bonded channels, the latency imbalance being a difference in latency between the respective upstream and downstream channels caused by a difference in multiplexing or demultiplexing path length of the respective upstream and downstream channels; and forming (504) the one or more fiber paddings based on the one or more determined padding lengths.

20. the padding unit comprises a plurality of fiber paddings, each fiber padding for a respective one of at least a subset of a plurality of pairs of coupled channels in the optical device; 20. The method of claim 19, wherein the padding lengths of fiber in each of the plurality of fiber paddings are configured to offset at least a portion of the latency imbalance in the respective pair of bonded channels such that the difference in latency imbalance across the pair of bonded channels is reduced.

21. the padding unit comprises a plurality of fiber paddings, each fiber padding for a respective one of at least a subset of a plurality of pairs of coupled channels in the optical device; 20. The method of claim 19, wherein a fiber padding length in each of the plurality of fiber paddings is configured to offset at least a portion of a latency in at least one channel of the respective pair of bonded channels such that latency across all channels in the plurality of pairs of bonded channels is equalized to a common value.

22. determining the padding length of each fiber padding; a nominal splice length of the fibers in each said pair of coupled channels; and a measured difference in path length of the upstream channel and the downstream channel in each pair of coupled channels following fiber splicing in the respective pair of coupled channels; and a measured delay in the upstream and downstream channels of the respective pairs of bonded channels, the delay caused by the path length of the respective upstream and downstream channels; and The method of claim 19, based on one of:

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