Apparatus, method and optical filter for optical communication

Abstract

The embodiment of the invention relates to a method and device for optical communication, an optical filter and a computer readable storage medium. In an example method, a first apparatus sends initialization information to a second apparatus over an optical signal having a fixed optical wavelength, the initialization information including at least synchronization information for a network device associated with the second apparatus. The first device selects, for the second device, a tunable optical wavelength for optical communication of the second device. The first device also transmits tunable optical wavelength information for the tunable optical wavelength to the second device via an optical signal having a fixed optical wavelength. In this manner, distribution of common local oscillator synchronization information can be supported, and enhanced filtering performance is achieved.

Description

Technical Field

[0001] Example embodiments of the present disclosure relate to the field of communications, and more particularly to methods, devices, optical filters, and computer-readable storage media for optical communications. Background Art

[0002] The fifth generation (5G) mobile network has been deployed worldwide to achieve large-scale connectivity, ultra-high reliability, and low latency. Current 5G mobile networks have difficulty in providing better coverage and balanced user performance in a wide coverage area. In order to improve the performance of cell-edge users, Cellular-free Massive Multiple Input Multiple Output (CF-mMIMO) has been considered as a possible candidate technology for the upcoming sixth generation (6G) network. A key challenge of CF-mMIMO is fronthaul, which is responsible for the transmission and synchronization of large amounts of data between the central processing unit (CPU) and distributed access points (APs).

[0003] However, in order to optimize the performance of fronthaul networks such as 6G networks, or more generally, to optimize the performance of communication networks, some technologies related to optical communications require further research and enhancement. Summary of the invention

[0004] In general, example embodiments of the present disclosure provide methods, apparatuses, optical filters, and computer-readable storage media for optical communications.

[0005] In a first aspect of the present disclosure, a first device is provided, comprising: at least one processor and at least one memory, wherein the at least one memory stores instructions, which, when executed by the at least one processor, enable the first device to at least: send initialization information to a second device via an optical signal having a fixed optical wavelength, wherein the initialization information at least includes synchronization information for a network device associated with the second device; select a tunable optical wavelength for optical communication of the second device for the second device; and send tunable optical wavelength information for the tunable optical wavelength to the second device via the optical signal having the fixed optical wavelength.

[0006] In a second aspect of the present disclosure, a second device is provided, comprising: at least one processor and at least one memory, the at least one memory storing instructions, which, when executed by the at least one processor, causes the second device to at least: receive initialization information from a first device via an optical signal having a fixed optical wavelength, wherein the initialization information at least includes synchronization information for a network device associated with the second device; synchronize the network device based on the synchronization information; receive tunable optical wavelength information for a tunable optical wavelength for optical communication of the second device from the first device via an optical signal having a fixed optical wavelength; and configure tunable circuit parameters corresponding to the tunable optical wavelength based on the received tunable optical wavelength information for the tunable optical wavelength to generate an optical signal having a tunable optical wavelength for optical communication.

[0007] In a third aspect of the present disclosure, an optical filter is provided, comprising: a first resonator operating at a fixed optical wavelength; and a second resonator coupled to the first resonator, wherein the second resonator has tunable circuit parameters and is operable at an optical wavelength corresponding to the tunable circuit parameters.

[0008] In a fourth aspect of the present disclosure, a method is provided, comprising: sending initialization information to a second device via an optical signal having a fixed optical wavelength, wherein the initialization information includes at least synchronization information for a network device associated with the second device; selecting a tunable optical wavelength for optical communication of the second device for the second device; and sending tunable optical wavelength information for the tunable optical wavelength to the second device via an optical signal having a fixed optical wavelength.

[0009] In a fifth aspect of the present disclosure, a method is provided, comprising: receiving initialization information from a first device via an optical signal having a fixed optical wavelength, wherein the initialization information includes at least synchronization information for a network device associated with a second device; synchronizing the network device based on the synchronization information; receiving tunable optical wavelength information for a tunable optical wavelength for optical communication with the second device from the first device via an optical signal having a fixed optical wavelength; and configuring tunable circuit parameters corresponding to the tunable optical wavelength based on the received tunable optical wavelength information for the tunable optical wavelength to generate an optical signal with a tunable optical wavelength for optical communication.

[0010] In a sixth aspect of the present disclosure, a first device is provided, comprising: a component for sending initialization information to a second device via an optical signal having a fixed optical wavelength, wherein the initialization information includes at least synchronization information for a network device associated with the second device; a component for selecting a tunable optical wavelength for optical communication of the second device for the second device; and a component for sending tunable optical wavelength information for the tunable optical wavelength to the second device via the fixed optical wavelength.

[0011] In a seventh aspect of the present disclosure, a second device is provided, comprising: a component for receiving initialization information from a first device via an optical signal having a fixed optical wavelength, wherein the initialization information includes at least synchronization information for a network device associated with the second device; a component for synchronizing the network device based on the synchronization information; a component for receiving tunable optical wavelength information for optical communication of the second device from the first device; and a component for configuring tunable circuit parameters corresponding to the tunable optical wavelength based on the received tunable optical wavelength information for the tunable optical wavelength to generate an optical signal having a tunable optical wavelength for optical communication.

[0012] In an eighth aspect of the present disclosure, a computer-readable storage medium is provided, comprising program instructions, which, when executed by at least one processor, cause a device to at least perform: sending initialization information to a second device via an optical signal having a fixed optical wavelength, wherein the initialization information at least includes synchronization information for a network device associated with the second device; selecting a tunable optical wavelength for optical communication of the second device for the second device; and sending tunable optical wavelength information for the tunable optical wavelength to the second device via an optical signal having a fixed optical wavelength.

[0013] In a ninth aspect of the present disclosure, a computer-readable storage medium is provided, comprising program instructions, which, when executed by at least one processor, cause the device to at least perform: receiving initialization information from a first device via an optical signal having a fixed optical wavelength, wherein the initialization information at least includes synchronization information for a network device associated with a second device; synchronizing the network device based on the synchronization information; receiving tunable optical wavelength information for a tunable optical wavelength for optical communication with the second device from the first device via an optical signal having a fixed optical wavelength; and configuring tunable circuit parameters corresponding to the tunable optical wavelength based on the received tunable optical wavelength information for the tunable optical wavelength to generate an optical signal with a tunable optical wavelength for optical communication.

[0014] In a tenth aspect of the present disclosure, there is provided a computer program comprising instructions, which, when executed by a device, cause the device to at least: send initialization information to a second device via an optical signal having a fixed optical wavelength, wherein the initialization information at least includes synchronization information for a network device associated with the second device; select a tunable optical wavelength for optical communication of the second device for the second device; and send tunable optical wavelength information for the tunable optical wavelength to the second device via an optical signal having a fixed optical wavelength.

[0015] In an eleventh aspect of the present disclosure, there is provided a computer program comprising instructions, which, when executed by a device, causes the device to at least: receive initialization information from a first device via an optical signal having a fixed optical wavelength, wherein the initialization information at least includes synchronization information for a network device associated with a second device; synchronize the network device based on the synchronization information; receive tunable optical wavelength information for a tunable optical wavelength for optical communication with the second device from the first device via an optical signal having a fixed optical wavelength; and configure tunable circuit parameters corresponding to the tunable optical wavelength based on the received tunable optical wavelength information for the tunable optical wavelength to generate an optical signal with a tunable optical wavelength for optical communication.

[0016] In the twelfth aspect of the present disclosure, a first device is provided, comprising: a sending circuit, the sending circuit being configured to send initialization information to a second device via an optical signal having a fixed optical wavelength, wherein the initialization information at least includes synchronization information for a network device associated with the second device; a selection circuit, the selection circuit being configured to select a tunable optical wavelength for optical communication of the second device for the second device; and a sending circuit, the sending circuit being configured to send tunable optical wavelength information for the tunable optical wavelength to the second device via an optical signal having a fixed optical wavelength.

[0017] In the thirteenth aspect of the present disclosure, a second device is provided, comprising: a receiving circuit, the receiving circuit being configured to receive initialization information from the first device via an optical signal having a fixed optical wavelength, wherein the initialization information includes at least synchronization information for a network device associated with the second device; a synchronization circuit, the synchronization circuit being configured to synchronize the network device based on the synchronization information; a receiving circuit, the receiving circuit being configured to receive tunable optical wavelength information for a tunable optical wavelength for optical communication with the second device from the first device via an optical signal having a fixed optical wavelength; and a configuration circuit, the configuration circuit being configured to configure tunable circuit parameters corresponding to the tunable optical wavelength based on the received tunable optical wavelength information for the tunable optical wavelength to generate an optical signal with a tunable optical wavelength for optical communication.

[0018] It should be understood that the invention summary is not intended to identify the key or essential features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0020] Figure 1A shows an example communication network in which embodiments of the present disclosure may be implemented;

[0021] Figure 1B shows the synchronization problem in CF-mMIMO;

[0022] Figure 2 shows a process flow according to some example embodiments of the present disclosure;

[0023] Figure 3 A RoF node and an optical dual filter therein according to some example embodiments of the present disclosure are shown;

[0024] Figure 4A A schematic diagram showing the use of optical dual filters for CF-mMIMO ring fronthaul according to some example embodiments of the present disclosure;

[0025] Figure 4B A schematic diagram showing the use of optical dual filters for CF-mMIMO tree fronthaul according to some example embodiments of the present disclosure;

[0026] Figure 5 An example flow chart of using an optical dual filter for CF-mMIMO fronthaul according to some example embodiments of the present disclosure is shown;

[0027] Figure 6 A RoF node and an optical dual filter therein according to some example embodiments of the present disclosure are shown;

[0028] Fig. 7A and 7B shows performance evaluation of optical duplex filters according to some example embodiments of the present disclosure;

[0029] Figure 7C Performance evaluation of an optical doublet filter optimized by a neural network (NN) approach according to some example embodiments of the present disclosure is shown;

[0030] Fig.7D shows a layout design of a photonic integrated chip (PIC) of an optical double filter according to some example embodiments of the present disclosure;

[0031] Figure 8 An optical double filter according to some example embodiments of the present disclosure is shown;

[0032] Fig. 9 A flowchart showing a method implemented on a first device according to some example embodiments of the present disclosure is shown;

[0033] Fig.10 A flowchart showing a method implemented on a second device according to some example embodiments of the present disclosure is shown;

[0034] Fig.11 shows a simplified block diagram of a device suitable for implementing an embodiment of the present disclosure; and

[0035] Fig.12 A block diagram of an example computer-readable medium is shown in accordance with some embodiments of the present disclosure.

[0036] In the drawings, the same or similar reference numerals denote the same or similar elements. DETAILED DESCRIPTION

[0037] The principles and spirit of the present disclosure will be described below with reference to several exemplary embodiments shown in the accompanying drawings. It should be understood that these specific embodiments are described only to enable those skilled in the art to better understand and implement the present disclosure, and are not intended to limit the scope of the present disclosure in any way.

[0038] As used herein, the term "including" and similar terms should be understood as open inclusion, i.e., "including but not limited to". The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0039] As used herein, the term "determine" covers a variety of actions. For example, "determine" may include operation, calculation, processing, export, investigation, search (e.g., search in a table, a database or another data structure), ascertain, etc. In addition, "determine" may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), etc. In addition, "determine" may include parsing, selecting, selecting, establishing, etc. As used herein, "at least one of the following: " and "at least one of " and similar expressions, wherein a list of two or more elements is connected by "and" or "or", means at least any one of these elements, or at least any two or more of these elements, or at least all of them.

[0040] The term "circuitry" as used herein refers to one or more of: (a) a hardware circuit implementation only (such as an implementation of analog and / or digital circuitry only); and (b) a combination of hardware circuitry and software, such as (where applicable): (i) a combination of analog and / or digital hardware circuitry and software / firmware, and (ii) any portion of a hardware processor and software (including a digital signal processor, software, and memory that work together to enable an apparatus such as a RoF network element or other computing device to perform various functions); and (c) a hardware circuit and / or processor, such as a microprocessor or portion of a microprocessor, that requires software (e.g., firmware) for operation, but may be without software when software is not required for operation.

[0041] The definition of circuitry applies to all uses of this term in this application, including in any claims. As another example, the term "circuitry" as used herein also covers an implementation of only a hardware circuit or processor (or multiple processors), or a portion of a hardware circuit or processor, or accompanying software or firmware. For example, if applicable to a particular claim notation, the term "circuitry" also covers a baseband integrated circuit or a processor integrated circuit or a similar integrated circuit in a RoF network unit or other computing device.

[0042] Figure 1A 1 shows an example communication network 100 in which embodiments of the present disclosure may be implemented. Figure 1A As shown, the communication network 100 includes a central processing unit (CPU) 105, a first device 110, an optical distribution network (ODN) 115, second devices 120-1 and 120-2 (hereinafter collectively referred to as second devices 120), and access points (APs) 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 (hereinafter collectively referred to as AP 130). In some example embodiments, the first device 110 may include a radio over fiber (RoF) transceiver (TRx), and the second device 120 may include a RoF node. Therefore, for ease of description, in some example embodiments below, the first device 110 may also be directly referred to as a RoF TRx, and the second device 120 may also be directly referred to as a RoF node.

[0043] like Figure 1A As shown, the first device 110 and the second device 120 can communicate through the ODN 115. Therefore, between the first device 110 and the second device 120, optical communication transmission can be performed through the uplink from the second device 120 to the first device 110, and optical communication transmission can also be performed through the downlink from the first device 110 to the second device 120. It should be understood that although Figure 1A 1 , one first device 110 , two second devices 120 , and six APs 130 are shown. The communication network 100 may also include any number of first devices 110 , second devices 120 , and APs 130 .

[0044] As mentioned above, mature fronthaul technology is based on the Ethernet transport layer. Given that CF-mMIMO requires very high-quality carrier phase synchronization on a distributed radio frequency (RF) chain, fronthaul may be problematic because Ethernet-based frequency synchronization suffers from phase instability, which may significantly degrade the performance of CF-mMIMO. Advanced “over-the-air calibration” techniques can be used to mitigate the effects of phase drift, but may incur significant overhead. Direct distribution of common local oscillator (LO) synchronization information to large-scale APs is also a solution, but fronthaul technology does not support this approach. In addition, in CF-mMIMO, power consumption may grow indefinitely due to network densification, which requires a dynamic AP switch-ON / OFF (ASO) strategy based on business conditions.

[0045] It is best that the fronthaul network also supports dynamic switching, rather than just static point-to-point links, which would cause unnecessary energy waste. Many fronthaul-related studies focus on developing photonic integrated chip (PIC)-based transceivers, which have the characteristics of significantly low power consumption, low cost, fast response time, and small footprint. Many studies have used PIC devices with wavelength tunability to implement flexible optical nodes for 5G mobile fronthaul. Microring resonator (MRR)-based PIC solutions are one of the ways to implement dynamically configurable wavelength filters or add / drop devices. However, the above studies did not consider supporting the distribution of phase synchronization or LO synchronization information in CF-mMIMO fronthaul scenarios.

[0046] Figure 1B The synchronization problem in CF-mMIMO is shown. The CF-mMIMO fronthaul technology based on RoF TRx needs to solve the following challenges:

[0047] First, the current mature Ethernet-based frequency synchronization has a serious phase drift problem (for example, within 10 milliseconds, for a 10 GHz RF with 1 ppb stability, the phase drift is 2πΔft=36°). Even if advanced air interface calibration technology is introduced, it will bring significant overhead.

[0048] Second, for B5G / 6G CF-mMIMO fronthaul, PIC-based RoF TRx cannot support the distribution of common LO synchronization information.

[0049] Third, the traditional design approach of MRR-based PIC filters is difficult to scale and can only support very limited data wavelength tunability for B5G fronthaul (e.g., the design approach of MRR-based PIC filters only achieves 4 and 12 tunable wavelengths).

[0050] In view of this, an embodiment of the present application provides a scheme for optical communication using an optical double filter. In some example embodiments, a first device (e.g., RoF TRx) sends initialization information to a second device (e.g., RoF node) via an optical signal with a fixed optical wavelength, wherein the initialization information at least includes synchronization information for a network device associated with the second device; accordingly, the second device receives the initialization information and synchronizes the network device based on the synchronization information.

[0051] Further, the first device selects a tunable optical wavelength for optical communication of the second device for the second device, and sends tunable optical wavelength information for the tunable optical wavelength to the second device through an optical signal with the fixed optical wavelength; accordingly, the second device receives the tunable optical wavelength information for the tunable optical wavelength through the optical signal with the fixed optical wavelength, and configures the tunable circuit parameters corresponding to the tunable optical wavelength based on the tunable optical wavelength information for the tunable optical wavelength to generate an optical signal with the tunable optical wavelength for optical communication. The optical dual filter design proposed by this scheme can support the distribution of common LO synchronization information and achieve enhanced filtering performance.

[0052] The following will refer to Figures 2 to 12 Example embodiments of the present disclosure are described in detail.

[0053] Figure 2 FIG. 2 shows a process 200 according to some example embodiments of the present disclosure. Figure 1A Let's discuss the process 200. The process 200 may involve Figure 1A In addition, the first device 110 (eg, RoFTRx) and the second device 120 (eg, RoF node) shown in FIG. Figure 1A The process 200 discussed below also involves the CPU 105 connected to the first device 110 and the AP 130 connected to the second device 120. However, for ease of description, the CPU 105 and the AP 130 are described in detail below. Figure 2 Not shown.

[0054] like Figure 2 As shown, the first device 110 sends 202 initialization information 204 to the second device 120 via an optical signal having a fixed optical wavelength. The initialization information 204 at least includes synchronization information for a network device (eg, AP 130 ) associated with the second device 120 .

[0055] Accordingly, the second device 120 receives 206 initialization information 204 from the first device 110 via an optical signal having a fixed optical wavelength, the initialization information 204 including at least synchronization information for a network device (eg, the AP 130 ) associated with the second device 120 .

[0056] In some embodiments, the synchronization information for the network devices includes common local oscillator (LO) synchronization information.

[0057] The second device 120 synchronizes 208 the network device (eg, AP 130) based on the synchronization information. In some embodiments, the second device 120 phase-synchronizes the network device connected to the second device 120 based on the common local oscillator (LO) synchronization information.

[0058] The first device 110 selects 210 a tunable optical wavelength for optical communication of the second device 120 for the second device 120. In some embodiments, the selection of the tunable optical wavelength is based on a traffic condition of the network device, and the traffic condition of the network device is reported by the network device to a processing device (e.g., CPU 105) associated with the first device 110.

[0059] The first device 110 transmits 212 tunable optical wavelength information 214 for the tunable optical wavelength to the second device 120 via an optical signal having the fixed optical wavelength. In some embodiments, the tunable optical wavelength information 214 for the tunable optical wavelength includes scheduling information for the tunable optical wavelength.

[0060] In some embodiments, the first device 110 further sends the tunable circuit parameters to the second device 120 via an optical signal having a fixed optical wavelength. For example, the tunable circuit parameters may be included in the initialization information 204; or the tunable circuit parameters may be sent together with the tunable optical wavelength information 214 for the tunable optical wavelength; or the tunable circuit parameters may be sent separately. Accordingly, the second device 120 receives the tunable circuit parameters from the first device 110 via an optical signal having a fixed optical wavelength. In addition, the tunable circuit parameters may also be pre-stored or pre-configured on the second device 120.

[0061] Accordingly, the second device 120 receives 216 tunable optical wavelength information 214 for a tunable optical wavelength for optical communication of the second device 120 from the first device 110 via an optical signal having a fixed optical wavelength. Thereafter, the second device 120 configures 218 tunable circuit parameters corresponding to the tunable optical wavelength based on the tunable optical wavelength information for the tunable optical wavelength to generate an optical signal having the tunable optical wavelength for optical communication. In some embodiments, the tunable circuit parameters include a coupling coefficient of a directional coupler and a phase of a waveguide.

[0062] In some embodiments, the second device 120 sends a ready signal (e.g., a first ready signal) indicating that the tunable circuit parameters have been configured to the first device 110. Accordingly, the first device 110 receives the first ready signal from the second device 120 indicating that the second device 120 has configured the tunable circuit parameters, and based on receiving the first ready signal, sends a second ready signal to the processing device indicating that the second device 120 has configured the tunable circuit parameters.

[0063] Figure 3 FIG. 2 shows a RoF node 300 and an optical dual filter 310 therein according to some example embodiments of the present disclosure. Figure 3 The optical dual filter 310 shown can support the distribution of common LO synchronization information and achieve enhanced filtering performance for B5G / 6G green CF-mMIMO fronthaul. The present disclosure utilizes an optical dual filter in combination with a dual micro-ring resonator (MRR), which includes a fixed optical wavelength λ that supports the distribution of common LO synchronization information. 0 portion 320 (ie, the first portion) and the tunable data wavelength -λ t k Part 330 (i.e., the second part); wherein Figure 4A and Figure 4B As shown, the tunable data wavelength -λ t k is allocated to a specific RoF node k according to reported traffic conditions (e.g., according to an AP Switching On / Off (ASO) policy, where the ASO policy is based on the number and / or location of active user equipment (UE), etc.), where t represents the tunable optical wavelength and k represents the RoF node identifier (id). Figure 4A and Figure 4B As shown, the optical double filter proposed in the present disclosure can be used for the ring fronthaul 400A and the tree fronthaul 400B respectively.

[0064] Figure 5 An example flow chart 500 of using an optical dual filter (hereinafter referred to as a dual filter) for CF-mMIMO fronthaul according to some example embodiments of the present disclosure is shown. Figure 4A and Figure 4B An example flow chart 500 is described. Figure 5 As shown, the exemplary flowchart 500 includes at least an initialization process 510 and an access process 520. After initialization, the RoF TRx 501 will use a fixed optical wavelength λ 0 Broadcast initialization information, the initialization information includes common LO synchronization information and a data table, wherein the data table includes a data-λ tk The proposed dual filter consists of a fixed optical wavelength λ 0 part (ie, the first part) and the tunable data wavelength -λ t k Part (i.e., the second part), the initialization and configuration of the dual filter includes the following two processes:

[0065] First, the initialization process 510. Before operation, the RoF TRx 501 and the RoF node 502 perform initialization operations 511a and 511b respectively. For example, during the initialization process 510, at 511b, the first part of the dual filter of each RoF node 502 should be configured to a fixed optical wavelength λ 0 (e.g., 1310 nm), and the second part of the dual filter of each RoF node 502 should be t k Set to default lambda 1 (e.g., 1550 nm) for normal operation. After initialization operations 511a and 511b, RoF TRx 501 will 0 Broadcasting initialization information to all RoF nodes 502 (512). For example, operation 512 may correspond to Figure 4A and Figure 4B Operation 412 in. The initialization information includes common LO synchronization information. In the first embodiment, the initialization information may also include a data table, wherein the data table includes a tunable circuit parameter param_cir.

[0066] After that, based on the fixed light wavelength λ 0 Filtering to configure common LO synchronization information (513), each AP 503 can perform synchronization (514). For example, operation 513 can correspond to Figure 4A and Figure 4B In operation 413, one or more of the RoF nodes 402-1, 402-2, 402-3, 402-4, 402-5, 402-6, 402-7 may be configured to have a fixed optical wavelength λ 0 The common LO synchronization information is configured so that a corresponding one or more APs among the APs 403-1, 403-2, 403-3, 403-4, 403-5, 403-6, 403-7 perform synchronization.

[0067] Second, access process 520. During access process 520, each AP 503 will report the traffic status to CPU 105 (521). Thereafter, after the cell scheduler of CPU 105 performs cell scheduling (522), through the operation of the collaborative transmission interface (CTI) (523), RoF TRx 501 will perform enhanced collaborative dynamic bandwidth allocation (eCoDBA) operation (524), which includes selecting the preferred optical tunable wavelength λ for a specific RoF node 502. t k .

[0068] Thus, the preferred tunable data wavelength -λ selected by the RoF TRx 501 is included t k The eCoDBA information of the RoF TRx 501 will be distributed and sent to the corresponding RoF node 502 (525). In the second embodiment, the data table (the data table includes the tunable circuit parameter param_cir) can be sent together with the eCoDBA information. In the third embodiment, the data table (the data table includes the tunable circuit parameter param_cir) can be sent separately. In the fourth embodiment, the RoF TRx 501 only sends the data related to the preferred tunable wavelength -λ to the corresponding RoF node 502. t k Corresponding tunable circuit parameters. It should be noted that a combination of the first, second, third and fourth embodiments is also possible. In addition, the tunable circuit parameter param_cir may also be pre-stored or pre-configured on the RoF node 502.

[0069] For example, operation 525 may correspond to Figure 4A and Figure 4B Operation 425 in which the RoF TRx 401 may send eCoDBA information including a new tunable data wavelength -λ to one or more of the RoF nodes 402-1, 402-2, 402-3, 402-4, 402-5, 402-6, 402-7. t k .

[0070] Typically, the eCoDBA information may include tunable optical wavelength information, that is, the eCoDBA information may include information related to the preferred tunable data wavelength -λ t k Thereafter, according to the first, second and third implementations above, the RoF node 502 will configure the tunable data wavelength -λ through the data table. t kFiltering part (526). That is, the RoF node 502 will select the preferred tunable data wavelength -λ from the data table according to the system scheduling information. t k The corresponding tunable circuit parameters and the preferred tunable data wavelength -λ t k The corresponding tunable circuit parameters are used to configure the tunable data wavelength -λ t k Filtering part.

[0071] In comparison, according to the fourth embodiment, the RoF node 502 directly transmits the data to the preferred tunable data wavelength -λ. t k The corresponding tunable circuit parameters are used to configure the tunable data wavelength -λ t k Filtering part.

[0072] For example, operation 526 may correspond to Figure 4A and Figure 4B Operation 426 in which one or more of the RoF nodes 402-1, 402-2, 402-3, 402-4, 402-5, 402-6, 402-7 can configure the tunable data wavelength -λ through the data table t k After configuration, RoF node 502 may send a “ready” signal to RoF TRx 501 (527), and RoF TRx 501 sends a “ready” signal to CPU 105 based on the “ready” signal (528).

[0073] Thereafter, upon receiving a “ready” signal from the RoF TRx 501, the CPU 105 starts sending the forwarding payload (530).

[0074] It should be noted that if Figure 5 As shown, the proposed dual filter can be implemented at each RoF node 502 near each AP 503 for distribution of common LO synchronization information and flexible filtering based on reported traffic conditions, with the goal of achieving very low power consumption and green CF-mMIMO fronthaul. Figure 3 As shown, the fixed light wavelength λ 0 The fixed wavelength λ of the light output by the portion 320 (ie, the first portion) 0The signal can be separated into two streams: the upper stream is used for the distribution of common LO synchronization information in the downlink (DL); the lower stream is reused in the uplink (UL) for ring fronthaul, but the lower stream is not required for tree fronthaul. In a more simplified example embodiment, such as tree fronthaul, the fixed optical wavelength λ 0 The fixed wavelength λ of the light output by the portion 320 (ie, the first portion) 0 The signal is only used for the distribution of common LO synchronization information. Figure 5 As shown, in the present disclosure, the tunable circuit parameter param_cir can be implemented in the RoF TRx 501 or the CPU 105 or the network computing unit by using a PyTorch-based TM After training, the data table including the tunable circuit parameters param_cir described above may be stored in the RoF TRx 501. If necessary, during the initialization process 510, the data table may also be stored in each RoF node 502.

[0075] Figure 6 FIG. 4 shows a RoF node 600 and an optical dual filter 610 (hereinafter referred to as a dual filter) therein according to some example embodiments of the present disclosure. Figure 6 As shown, the proposed dual filter includes a waveguide (WG) and a directional coupler (DC), which can be realized by an optical circuit using a suitable simulation tool. Here, the tunable circuit parameter param_cir can be expressed as the coupling coefficient γ of the directional coupler DC. t i and the even-numbered waveguides wg 2i The phase θ t 2i , where the odd-numbered waveguides wg 2i-1 The phase of is set to 0, and the index of the directional coupler dc / waveguide wg is denoted as i. After careful consideration and detailed evaluation, the fixed optical wavelength λ in the dual filter 0 portion 620 (ie, the first portion) and the tunable data wavelength -λ t k The number of loops in part 630 (i.e., the second part) can be set to 1 and 4 respectively. It should be noted that in order to achieve better filtering performance, the key parameter γ t i and θ t 2i It can be implemented in RoF TRx through PyTorch-based TM PIC optimization is used for training. Figure 6As shown, in each RoF node, the key parameter γ in the tunable circuit parameter param_cir is t i and θ t 2i The configured dual filters have been successfully verified using appropriate simulation tools.

[0076] Fig. 7A and Figure 7B shows performance evaluation of optical doublet filters according to some example embodiments of the present disclosure, Figure 7B yes Fig. 7A A magnified view of the tunable part of the Fig. 7A and 7B As shown, after verification based on appropriate simulation tools, the proposed optical double filter can support the use of fixed optical wavelength λ 0 Distribute common LO synchronization information and realize 32 channels of 50GHz tunable data wavelength-λ t k It is important to note that the proposed flexible optical dual filter is optimized by a neural network (NN) based approach with an optimal training loss of 0.00206, as shown in Figure 7C As shown. Figure 7C In this paper, a neural network (NN) based method is used to find the target tunable optical wavelength λ t k Optimization was achieved at 1550nm.

[0077] For the hardware implementation of the concept of the present disclosure, it is necessary to consider the actual PIC tape-out, especially for the tunable data wavelength -λ in the proposed optical double filter t k part (ie, the second part). Fig.7D A PIC layout design of an optical double filter according to some example embodiments of the present disclosure is shown. Fig.7D The possible PIC layout of the optical double filter shown is drawn using the open source EDA tool GDSfactory. t k Part (i.e., the second part), the trained parameters γ t i This can be achieved by a coupler based on the Mach-Zehnder-Interferometer (MZI), and the parameter θ t 2iThis can be achieved by using intracavity thermo-optically tuned phase shifters in each ring. It is important to note that the final device performance and stability may be sensitive to various factors. In order to map the machine learning optimized circuit parameters to the actual device configuration, waveguide-level physical simulation may be required to fully verify the PIC. In addition, further detailed tuning may be required to ensure that the foundry's process design kit supports the design.

[0078] For example, the advantages and application scenarios of the concepts of the embodiments of the present disclosure are embodied in but not limited to the following aspects:

[0079] First, the optical double filter of the embodiment of the present disclosure has a fixed optical wavelength λ 0 Partial and 32-way tunable data wavelength -λ t k As a part of this, it can support the distribution of common LO synchronization information and achieve enhanced filtering performance, with the goal of realizing B5G / 6G green CF-mMIMO fronthaul.

[0080] Second, the optical dual filter of the embodiment of the present disclosure can support 32 tunable data optical wavelengths λ through optimization based on a neural network (NN). t k .

[0081] Third, the optical dual filter of the disclosed embodiment can support the distribution of common LO synchronization information and excellent filtering performance for B5G / 6G green fronthaul or coherent / optical access / data center interconnect (DCI) systems (for example, B5G / 6G (such as cellular-free / distributed / extremely large-scale MIMO fronthaul / backhaul / midhaul), high-speed PON, and coherent / access / DCI systems) with extremely low power consumption.

[0082] The disclosed embodiments can be used in B5G / 6G fronthaul / backhaul / midhaul and high-speed coherent / PON / DCI product combinations (e.g., ROADM, flexible optical nodes) or any other related serial communications that require advanced signal filtering / switching / synchronization (e.g., signal filtering / switching). In addition, the disclosed embodiments also provide a new method for the distribution of common LO synchronization information and advanced optical filter design, which is very beneficial for low-power optical applications.

[0083] Figure 8 800 according to some example embodiments of the present disclosure. For example, the optical filter 800 may be an optical double filter. In some embodiments, the optical filter 800 may be Figure 1A In another embodiment, the optical filter 800 may also be implemented at the RoF node 120. Figure 1AThe RoF TRx 501, any other RoF node or RoF TRx or other device with similar functions is implemented.

[0084] like Figure 8 As shown, the optical filter 800 includes a first resonator 810, which operates at a fixed optical wavelength. Figure 3 In the case of the optical double filter 310 shown, the first resonator 810 may include a fixed optical wavelength λ 0 Part 320. The optical filter 800 includes Figure 6 In the case of the optical double filter 610 shown, the first resonator 810 may include a fixed optical wavelength λ 0 Part 620. The optical filter 800 includes Fig.7D In the case of the optical double filter shown, the first resonator 810 may include Fig.7D The fixed light wavelength portion is shown.

[0085] The optical filter 800 further includes a second resonator 820 coupled to the first resonator 810, the second resonator 820 having tunable circuit parameters and operable at an optical wavelength corresponding to the tunable circuit parameters. Figure 3 In the case of the optical double filter 310 shown, the second resonator 820 may include a tunable data wavelength -λ t k Part 330. The optical filter 800 includes Figure 6 In the case of the optical dual filter 610 shown, the second resonator 820 may include a tunable data wavelength -λ t k Part 630. The optical filter 800 includes Fig.7D In the case of the optical double filter shown, the second resonator 820 may include Fig.7D The tunable optical wavelength portion is shown.

[0086] In some embodiments, the input light of the first resonator 810 is connected to the optical distribution network ODN, the output light of the first resonator 810 is connected to the optical-to-electrical converter, and the output light of the second resonator 820 is connected to the optical-to-electrical converter. For example, the optical distribution network ODN can be as follows: Figure 1A An optical distribution network (ODN) 115 is shown.

[0087] In some embodiments, the first resonator 810 includes a micro-ring resonator composed of a directional coupler and a waveguide.

[0088] In some embodiments, the second resonator 820 includes a plurality of microring resonators, each of the plurality of microring resonators is composed of a directional coupler and a waveguide, and the tunable circuit parameters include a coupling coefficient of the directional coupler and a phase of the waveguide. Figure 6 In the case of the optical dual filter 610 shown, the second resonator 820 may include a tunable data wavelength -λ t k Part 630, the number of micro-ring resonators included in the second resonator 820 can be tunable to a data wavelength -λ t k The number of rings in section 630 (in Figure 6 4), and the coupling coefficient of the directional coupler and the phase of the waveguide can be set as follows: Figure 6 The coupling coefficient γ of the directional coupler dc is shown t i and the phase of the waveguide wg, where the even-numbered waveguide wg 2i The phase is θ t 2i And the odd-numbered waveguides wg 2i-1 The phase is set to 0.

[0089] Fig. 9 A schematic flow chart of a method 900 implemented on a first device according to some example embodiments of the present disclosure is shown. In some embodiments, the method 900 may be implemented on a first device. Figure 1A The method 900 is implemented at the first device 110. In other embodiments, the method 900 may also be implemented at any other first device or other equipment with similar functions.

[0090] At block 910, the first device 110 transmits initialization information to the second device 120 via an optical signal having a fixed optical wavelength, the initialization information including at least synchronization information for a network device associated with the second device 120. At block 920, the first device 110 selects a tunable optical wavelength for optical communication of the second device 120. At block 930, the first device 110 transmits tunable optical wavelength information for a tunable optical wavelength to the second device 120 via an optical signal having a fixed optical wavelength.

[0091] In some embodiments, the synchronization information for the network devices includes common local oscillator synchronization information.

[0092] In some embodiments, the first device further transmits the tunable circuit parameter to the second device via an optical signal having a fixed optical wavelength, and the tunable optical wavelength information for the tunable optical wavelength includes scheduling information for the tunable optical wavelength.

[0093] In some embodiments, the selection of the tunable optical wavelength is based on a traffic condition of the network device, and the traffic condition of the network device is reported by the network device to a processing device associated with the first apparatus.

[0094] In some embodiments, the first device is further configured to: receive a first ready signal from the second device indicating that the second device has configured the tunable circuit parameters; and based on receiving the first ready signal, send a second ready signal to the processing device indicating that the second device has configured the tunable circuit parameters.

[0095] In some embodiments, the first device comprises a radio over fiber RoF transceiver unit and the second device comprises a radio over fiber RoF node unit.

[0096] In some embodiments, the tunable circuit parameters include a coupling coefficient of a directional coupler and a phase of a waveguide.

[0097] Fig.10 A schematic flow chart of a method 1000 implemented on a second device according to some example embodiments of the present disclosure is shown. In some embodiments, the method 1000 may be implemented on a second device. Figure 1A The method 1000 may be implemented at the second device 120. In another embodiment, the method 1000 may also be implemented at any other second device or other equipment with similar functions.

[0098] In block 1010, the second device 120 receives initialization information from the first device 110 through an optical signal having a fixed optical wavelength, wherein the initialization information includes at least synchronization information for a network device associated with the second device 120. In block 1020, the second device 120 synchronizes the network device based on the synchronization information. In block 1030, the second device 120 receives tunable optical wavelength information for a tunable optical wavelength for optical communication of the second device 120 from the first device 110 through an optical signal having a fixed optical wavelength. In block 1040, the second device 120 configures a tunable circuit parameter corresponding to the tunable optical wavelength based on the received tunable optical wavelength information for the tunable optical wavelength to generate an optical signal having a tunable optical wavelength for optical communication.

[0099] In some embodiments, the initialization information includes common local oscillator synchronization information, and the second device phase synchronizes a network device connected to the second device based on the common local oscillator synchronization information.

[0100] In some embodiments, the second device is further caused to receive the tunable circuit parameter from the first device via an optical signal having a fixed optical wavelength, and the tunable optical wavelength information for the tunable optical wavelength includes scheduling information for the tunable optical wavelength.

[0101] In some embodiments, the tunable optical wavelength is selected by the first device for the second device based on traffic conditions of a network device reported to the first device.

[0102] In some embodiments, the second device is further caused to: send a ready signal to the first device indicating that the tunable circuit parameters have been configured.

[0103] In some embodiments, the first device comprises a radio over fiber RoF transceiver unit and the second device comprises a radio over fiber RoF node unit.

[0104] In some embodiments, the tunable circuit parameters include a coupling coefficient of a directional coupler and a phase of a waveguide.

[0105] In some embodiments, the first device capable of executing method 900 (for example, implemented at first device 110) may include a component for executing each step of method 900. The component may be implemented in any suitable form. For example, the component may be implemented in a circuit or a software module.

[0106] In some embodiments, the first device may include a component for sending initialization information to the second device via an optical signal having a fixed optical wavelength, the initialization information including at least synchronization information for a network device associated with the second device. The first device may also include a component for selecting a tunable optical wavelength for optical communication of the second device for the second device. The first device may also include a component for sending tunable optical wavelength information for a tunable optical wavelength to the second device via an optical signal having a fixed optical wavelength.

[0107] In some embodiments, the synchronization information for the network devices includes common local oscillator synchronization information.

[0108] In some embodiments, the first device may further include means for transmitting the tunable circuit parameter to the second device via an optical signal having a fixed optical wavelength, and the tunable optical wavelength information for the tunable optical wavelength includes scheduling information for the tunable optical wavelength.

[0109] In some embodiments, the selection of the tunable optical wavelength is based on a traffic condition of the network device, and the traffic condition of the network device is reported by the network device to a processing device associated with the first apparatus.

[0110] In some embodiments, the first device may also include: a component for receiving a first ready signal from the second device indicating that the second device has configured the tunable circuit parameters; and a component for sending a second ready signal to the processing device indicating that the second device has configured the tunable circuit parameters based on receiving the first ready signal.

[0111] In some embodiments, the first device comprises a radio over fiber RoF transceiver unit and the second device comprises a radio over fiber RoF node unit.

[0112] In some embodiments, the tunable circuit parameters include a coupling coefficient of a directional coupler and a phase of a waveguide.

[0113] In some embodiments, the second device capable of executing method 1000 (for example, implemented at second device 120) may include a component for executing each step of method 1000. The component may be implemented in any suitable form. For example, the component may be implemented in a circuit or a software module.

[0114] In some embodiments, the second device may include a component for receiving initialization information from the first device via an optical signal having a fixed optical wavelength, wherein the initialization information includes at least synchronization information for a network device associated with the second device. The second device may also include a component for synchronizing the network device based on the synchronization information. The second device may also include a component for receiving tunable optical wavelength information for a tunable optical wavelength for optical communication of the second device from the first device via an optical signal having a fixed optical wavelength. The second device may also include a component for configuring a tunable circuit parameter corresponding to the tunable optical wavelength based on the received tunable optical wavelength information for the tunable optical wavelength to generate an optical signal with a tunable optical wavelength for optical communication.

[0115] In some embodiments, the initialization information includes common local oscillator synchronization information, and the second device phase synchronizes a network device connected to the second device based on the common local oscillator synchronization information.

[0116] In some embodiments, the second device may further include means for receiving the tunable circuit parameter from the first device via an optical signal having a fixed optical wavelength, and the tunable optical wavelength information for the tunable optical wavelength includes scheduling information for the tunable optical wavelength.

[0117] In some embodiments, the tunable optical wavelength is selected by the first device for the second device based on traffic conditions of a network device reported to the first device.

[0118] In some embodiments, the second device may further include: means for sending a ready signal to the first device indicating that the tunable circuit parameters have been configured.

[0119] In some embodiments, the first device comprises a radio over fiber RoF transceiver unit, and the device comprises a radio over fiber RoF node unit.

[0120] In some embodiments, the tunable circuit parameters include a coupling coefficient of a directional coupler and a phase of a waveguide.

[0121] Fig.11 1 is a simplified block diagram of an electronic device 1100 suitable for implementing an embodiment of the present disclosure. The device 1100 may be provided to implement a communication device, such as the first device 110 and the second device 120 as shown in FIG. 1. As shown, the device 1100 includes one or more processors 1110, one or more memories 1120 coupled to the processor 1110, and one or more communication modules 1140 coupled to the processor 1110.

[0122] The communication module 1140 is used for two-way communication. For example, the communication module 1140 may include a transmitter, a receiver, or a transceiver used in the embodiments of the present disclosure. The communication interface may represent any interface necessary for communicating with other network elements.

[0123] Processor 1110 may be of any type suitable for the local technology network and may include, but is not limited to, one or more of a general purpose computer, a special purpose computer, a microcontroller, a digital signal controller (DSP), and a controller-based multi-core controller architecture. Device 1100 may have multiple processors, such as application specific integrated circuit chips, which are time-slaved to a clock synchronized with a main processor.

[0124] The memory 1120 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 1124, erasable programmable read-only memory (EPROM), flash memory, hard disk, compact disk (CD), digital video disk (DVD), and other magnetic storage and / or optical storage. Examples of volatile memories include, but are not limited to, random access memory (RAM) 1122 and other volatile memories that do not persist over the duration of a power outage.

[0125] Computer program 1130 includes computer executable instructions executed by associated processor 1110. Program 1130 may be stored in ROM 1120. Processor 1110 may perform any suitable actions and processes by loading program 1130 into RAM 1120.

[0126] The embodiments of the present disclosure can be implemented with the help of program 1130, so that the device 1100 can execute the Figures 2 to 10 Any process of the present disclosure discussed. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0127] In some embodiments, the program 1130 may be tangibly embodied in a computer-readable medium that may be included in the device 1100 (such as in the memory 1120) or other storage device accessible by the device 1100. The program 1130 may be loaded from the computer-readable medium to the RAM 1122 for execution. The computer-readable medium may include any type of tangible non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc.

[0128] Fig.12 An example of a computer readable medium 1200 in the form of a CD or DVD is shown. The computer readable medium has a program 1230 stored thereon.

[0129] In general, various embodiments of the present disclosure may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software, which may be performed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of the present disclosure are shown and described as block diagrams, flow charts, or using some other graphical representation, it should be understood that the blocks, devices, systems, techniques, or methods described herein may be implemented as, by way of non-limiting example, hardware, software, firmware, dedicated circuits or logic, general purpose hardware or a controller or other computing device, or some combination thereof.

[0130] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer executable instructions, such as instructions included in a program module, which are executed in a device on a real or virtual processor of a target to perform the above-referenced Fig. 9 and Fig.10 Methods 900 and 1000. Typically, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functionality of program modules can be combined or divided between program modules as needed. Machine executable instructions for program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in local and remote storage media.

[0131] The computer program code for realizing the method of the present disclosure can be written in one or more programming languages. These computer program codes can be provided to the processor of general-purpose computer, special-purpose computer or other programmable data processing device, so that the program code, when being executed by computer or other programmable data processing device, causes the function / operation specified in flow chart and / or block diagram to be implemented. The program code can be executed completely on computer, partly on computer, as independent software package, partly on computer and partly on remote computer or completely on remote computer or server.

[0132] In the context of the present disclosure, computer program codes or related data may be carried by any appropriate carrier to enable a device, apparatus or processor to perform the various processes and operations described above. Examples of carriers include signals, computer readable media, and the like. Examples of signals may include electrical, optical, radio, acoustic or other forms of propagation signals, such as carrier waves, infrared signals, and the like.

[0133] A computer-readable medium may be any tangible medium containing or storing a program for or about an instruction execution system, device or equipment. A computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. A computer-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, device or equipment, or any suitable combination thereof. A more detailed example of a computer-readable storage medium includes an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical storage device, a magnetic storage device, or any suitable combination thereof. As used herein, the term "non-transient" or "non-transient" is a limitation on the medium itself (i.e., tangible, not a signal), rather than a limitation on the persistence of data storage (e.g., RAM and ROM).

[0134] In addition, although the operation of the method of the present disclosure is described in a particular order in the accompanying drawings, this does not require or imply that these operations must be performed in this particular order, or that all the operations shown must be performed to achieve the desired result. On the contrary, the steps depicted in the flow chart can change the order of execution. Additionally or alternatively, some steps can be omitted, multiple steps can be combined into one step for execution, and / or one step can be decomposed into multiple steps for execution. It should also be noted that the features and functions of two or more devices according to the present disclosure can be embodied in one device. Conversely, the features and functions of a device described above can be further divided into being embodied by multiple devices.

[0135] Although the present disclosure has been described with reference to several specific embodiments, it should be understood that the present disclosure is not limited to the specific embodiments disclosed. The present disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A first device, comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the first device to at least: sending initialization information to the second device via an optical signal having a fixed optical wavelength, wherein the initialization information at least includes synchronization information for a network device associated with the second device; selecting, for the second device, a tunable optical wavelength for optical communication with the second device; and The tunable optical wavelength information for the tunable optical wavelength is transmitted to the second device through an optical signal having the fixed optical wavelength. 2 . The first apparatus according to claim 1 , wherein the synchronization information for the network device comprises common local oscillator synchronization information.

3. The first device according to claim 1 or 2, wherein the first device is further caused to send a tunable circuit parameter to the second device through an optical signal having the fixed optical wavelength, and the tunable optical wavelength information for the tunable optical wavelength includes scheduling information for the tunable optical wavelength.

4. The first apparatus according to any one of claims 1-3, wherein the selection of the tunable optical wavelength is based on a traffic condition of the network device, and the traffic condition of the network device is reported by the network device to a processing device associated with the first apparatus.

5. The first device according to claim 3, wherein the first device is further configured to: receiving a first ready signal from the second device indicating that the second device has configured the tunable circuit parameters; and Based on receiving the first ready signal, a second ready signal is sent to the processing device indicating that the second apparatus has configured the tunable circuit parameters.

6. The first device according to any one of claims 1-5, wherein the first device comprises a Radio over Fiber RoF transceiver unit, and the second device comprises a Radio over Fiber RoF node unit.

7. The first device according to claim 3 or 5, wherein the tunable circuit parameters include a coupling coefficient of a directional coupler and a phase of a waveguide.

8. A second device, comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the second device to at least: receiving initialization information from a first device via an optical signal having a fixed optical wavelength, wherein the initialization information includes at least synchronization information for a network device associated with the second device; synchronizing the network device based on the synchronization information; receiving, from the first device through the optical signal having the fixed optical wavelength, tunable optical wavelength information for a tunable optical wavelength for optical communication with the second device; as well as A tunable circuit parameter corresponding to the tunable optical wavelength is configured based on the received tunable optical wavelength information for the tunable optical wavelength to generate an optical signal having the tunable optical wavelength for optical communication. 9 . The second apparatus of claim 8 , wherein the initialization information comprises common local oscillator synchronization information, and wherein the second apparatus phase-synchronizes the network device connected to the second apparatus based on the common local oscillator synchronization information.

10. The second device according to claim 8 or 9, wherein the second device is further caused to receive a tunable circuit parameter from the first device through an optical signal having the fixed optical wavelength, and the tunable optical wavelength information for the tunable optical wavelength includes scheduling information for the tunable optical wavelength.

11. The second device according to any one of claims 8 to 10, wherein the tunable optical wavelength is selected by the first device for the second device based on a traffic condition of a network device reported to the first device.

12. The second device according to claim 11, wherein the second device is further caused to: A ready signal is sent to the first device indicating that the tunable circuit parameters have been configured.

13. The second device according to any one of claims 8 to 12, wherein the first device comprises a Radio over Fiber RoF transceiver unit, and the second device comprises a Radio over Fiber RoF node unit.

14. The second device according to any one of claims 8 to 13, wherein the tunable circuit parameters include a coupling coefficient of a directional coupler and a phase of a waveguide.

15. An optical filter comprising: a first resonator operating at a fixed optical wavelength; as well as A second resonator is coupled to the first resonator, wherein the second resonator has tunable circuit parameters and is operable at a wavelength of light corresponding to the tunable circuit parameters.

16. The optical filter according to claim 15, wherein input light of the first resonator is connected to an optical distribution network (ODN), wherein output light of the first resonator is connected to an optical-to-electrical converter, and wherein output light of the second resonator is connected to the optical-to-electrical converter.

17. The optical filter according to claim 15, wherein the first resonator comprises a micro-ring resonator composed of a directional coupler and a waveguide.

18. The optical filter according to claim 15, wherein the second resonator comprises a plurality of microring resonators, each of the plurality of microring resonators being composed of a directional coupler and a waveguide, and wherein the tunable circuit parameter comprises a coupling coefficient of the directional coupler and a phase of the waveguide.

19. A method comprising: sending initialization information to the second device via an optical signal having a fixed optical wavelength, wherein the initialization information at least includes synchronization information for a network device associated with the second device; selecting, for the second device, a tunable optical wavelength for optical communication with the second device; and The tunable optical wavelength information for the tunable optical wavelength is transmitted to the second device through an optical signal having the fixed optical wavelength.

20. A method comprising: receiving initialization information from a first device via an optical signal having a fixed optical wavelength, wherein the initialization information includes at least synchronization information for a network device associated with the second device; synchronizing the network device based on the synchronization information; receiving, from the first device through the optical signal having the fixed optical wavelength, tunable optical wavelength information for a tunable optical wavelength for optical communication with the second device; as well as A tunable circuit parameter corresponding to the tunable optical wavelength is configured based on the received tunable optical wavelength information for the tunable optical wavelength to generate an optical signal having the tunable optical wavelength for optical communication.

21. A first device, comprising: means for sending initialization information to a second device via an optical signal having a fixed optical wavelength, wherein the initialization information comprises at least synchronization information for a network device associated with the second device; means for selecting, for said second device, a tunable optical wavelength for optical communication of said second device; as well as means for transmitting tunable optical wavelength information for the tunable optical wavelength to the second device via the fixed optical wavelength.

22. A second device, comprising: means for receiving initialization information from a first device via an optical signal having a fixed optical wavelength, wherein the initialization information comprises at least synchronization information for a network device associated with the second device; means for synchronizing the network device based on the synchronization information; for receiving, from the first device through an optical signal having the fixed optical wavelength, tunable optical wavelength information for a tunable optical wavelength for optical communication with the second device; as well as Means for configuring a tunable circuit parameter corresponding to the tunable optical wavelength based on the received tunable optical wavelength information for the tunable optical wavelength to generate an optical signal having the tunable optical wavelength for optical communication.

23. A computer-readable storage medium comprising program instructions, which, when executed by at least one processor, cause an apparatus to at least perform the method according to claim 21 or 22.

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