Patent Description:
An existing Dense Wavelength Division Multiplexing (DWDM) system mostly adopts a channel spacing of <NUM> or <NUM> and thus is actually a fixed-grid Wavelength Division Multiplexing (WDM) system. With the development of ultra-high-speed <NUM>/B100G WDM transmission network and Automatically Switched Optical Network (ASON)/Software Defined Optical Network (SDON) technologies, a traditional WDM system is facing challenges in spectrum utilization and flexibility, and a demand is created for a flexible-grid WDM system that supports different channel spacings and transmission rates and has a channel spacing dynamically settable as desired.

The Flexible Grid technology was first standardized by the International Telecommunication Union-T (ITU-T) G. <NUM> standard in <NUM>. In the standard, the nominal central frequencies of normative frequency slots are <NUM> THz + n × <NUM>. The current mainstream WSS manufacturers all introduce WSS modules having a channel spacing of <NUM> or <NUM>, which achieves the quasi-Nyquist WDM transmission scheme having a higher spectral efficiency. For example, <NUM> Polarization Multiplexed Quadrature Phase Shift Keying (PM-QPSK) traffic optical signals (containing <NUM>% forward error correction (FEC) overhead) having a baud rate of about <NUM> Gbaud are transmitted in channels having a channel spacing of <NUM>. This method can further reduce channel spacings of a WDM system, thereby improving the spectral efficiency of the C-band in an optical fiber system and expanding the system transmission capacity.

Nevertheless, in a practical engineering application, a network structure composed of multiple Flex reconfigurable optical add-drop multiplexer (ROADM) sites exists in a network. As shown in <FIG>, it illustrates a scenario that Long-span end-to-end traffic signal light penetrates cascaded ROADM sites in a transmission link. As shown in <FIG>, both penetrating traffic light and add-drop traffic light at ROADM sites require cross-scheduling control by WSSs. The ROADM sites shown in <FIG> are typical two-dimensional ROADM site structures. WSSs in the straight-through direction of the ROADM sites cause filtering damage to the penetrating traffic light. Particularly in the quasi-Nyquist WDM scheme, a signal spectral bandwidth is close to a WSS channel bandwidth. In this manner, the receptivity severely deteriorates after the absorption spectrum is filtered by cascaded WSSs. This is mainly because the high-frequency components of the spectrum are significantly suppressed after being filtered by the cascaded WSSs. Thus, a large error occurs in the phase detection in the clock extraction algorithm in the receiver, and the clock jitter or extraction failure leads to a positional deviation in data recovery. As a result, the transmission traffic is interrupted.

No effective solution has been proposed to address the problem in which the performance of a receiver deteriorates after filtered optical signals enter the receiver because cascaded WSSs cause filtering damage to the optical signals in the related art. <CIT> introduces about a WSS for shaping optical signals. <CIT> introduces about a method for reducing crosstalk among subcarriers of a super-channel. <CIT> introduces about a method for channel additions over multiple cascaded optical nodes. <NPL> introduces about global WSS-based equalization strategies for SDN metropolitan mesh optical networks. <CIT> introduces about a transmission device that can suppress a deteriorated transmission characteristic of a control target super channel.

Embodiments of the present invention provide a method and device for controlling the WSS channel attenuation parameter and a storage medium to solve at least the problem in which the performance of a receiver deteriorates after filtered optical signals enter the receiver because cascaded WSSs cause filtering damage to the optical signals in the related art.

Through embodiments of the present invention, the following operations are performed for each WSS module in a cascaded WSS system: inputting white noise to the channel of each WSS module and adjusting the attenuation parameters of all slices of the channel according to a predefined rule such that the flatness of the output spectrum of the white noise is less than a first threshold; and calculating the average value of the adjusted attenuation parameters of the slices of a plurality of WSS modules and controlling the WSS channel attenuation parameter of each WSS module based on the average value. The preceding solution solves the problem in which the performance of a receiver deteriorates after filtered optical signals enter the receiver because cascaded WSSs cause filtering damage to the optical signals in the related art, thereby effectively reducing filtering damage when the optical signals pass through the cascaded WSSs and improving the performance of the receiver.

The drawings described herein are used to provide a further understanding of the present invention and form a part of the present application. The illustrative embodiments and the description thereof in the present invention are used to explain the present invention and not to limit the present invention improperly. In the drawings:.

Hereinafter, the present invention will be described in detail with reference to drawings and in conjunction with embodiments. It is to be noted that if not in collision, the embodiments described herein and the features in the embodiments may be combined with each other.

It is to be noted that the terms such as "first" and "second" in the description, claims and drawings of the present invention are used to distinguish between similar objects and are not necessarily used to describe a particular order or sequence.

This embodiment provides a method for controlling the WSS channel attenuation parameter. <FIG> is a flowchart of the method for controlling the WSS channel attenuation parameter according to an embodiment of the present invention. As shown in <FIG>, the method includes the steps S302 and S304 below.

In step S302, for each WSS module in a cascaded WSS system, white noise is input to the channel of each WSS module and the attenuation parameters of all slices of the channel are adjusted according to a predefined rule such that the flatness of the output spectrum of the white noise is less than a first threshold.

In step S304, the average value of the adjusted attenuation parameters of the slices of a plurality of WSS modules is calculated and the WSS channel attenuation parameter of each WSS module is controlled based on the average value.

Through the preceding steps, the following operations are performed for each WSS module in a cascaded WSS system: inputting white noise to the channel of each WSS module and adjusting the attenuation parameters of all slices of the channel according to a predefined rule such that the flatness of the output spectrum of the white noise is less than a first threshold; and calculating the average value of the adjusted attenuation parameters of the slices of a plurality of WSS modules and controlling the WSS channel attenuation parameter of each WSS module based on the average value. The preceding solution solves the problem in which the performance of a receiver deteriorates after filtered optical signals enter the receiver because cascaded WSSs cause filtering damage to the optical signals in the related art, thereby effectively reducing filtering damage when the optical signals pass through the cascaded WSSs and improving the performance of the receiver. Step S302 can be performed in multiple manners during the actual operation. One manner is provided in this embodiment of the present invention. The manner is described below.

The attenuation parameters of all slices of the channel are adjusted according to the predefined rule by using the solution below.

The attenuation parameters of the secondary edge slices of all slices are adjusted so that a first adjustment result is obtained; the attenuation parameters of one or more center slices of the channel are adjusted based on the first adjustment result so that a second adjustment result is obtained; and then other slices of all slices excluding the secondary edge slices and the center slices are adjusted based on the first adjustment result and the second adjustment result. That is, in this embodiment of the present invention, the attenuation parameters of the secondary edge slices of all slices, the attenuation parameters of the center slices of all slices and the attenuation parameters of other slices of all slices may be adjusted in sequence.

Based on the preceding solution, the detailed solution provided in this embodiment of the present invention is described below as to how to adjust the secondary edge slices, center slices and other slices of all slices.

By taking the central frequency fc of the channel as the central axis, the attenuation parameters of other slices are adjusted symmetrically according to the attenuation parameters of the secondary edge slices in the first adjustment result and the attenuation parameters of the center slices in the second adjustment result. The adjustment process for other slices is actually based on the adjustments to the secondary edge slices and the center slices. For example, in the case where there are currently <NUM> slices numbered <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> in sequence, first the attenuation parameter of secondary edge slice <NUM> is adjusted and then the attenuation parameter of center slice <NUM> is adjusted. Symmetrically, the attenuation parameter of slice <NUM> is mapped onto slice <NUM> on the right and the attenuation parameter of slice <NUM> is mapped onto slice <NUM> on the right. The preceding can be understood as symmetry from the left to the right. During the actual operation, symmetry from the right to the left is also feasible. This is not limited in this embodiment of the present invention. In addition, in this embodiment of the present invention, a manner is provided as below for calculating the average value described in step S304.

The attenuation parameters of first slices of all WSS modules are acquired separately and the average value of the attenuation parameters of the first slices of the all WSS modules is calculated. The attenuation parameters of second slices of all WSS modules to the attenuation parameter of N-th slices of all WSS module are acquired in sequence and the average value of the attenuation parameters of the second slices of the all WSS modules to the average value of the attenuation parameters of the N-th slices of the all WSS modules are calculated.

That is, in this embodiment of the present invention, the average value of the attenuation parameters of the first slices of the all WSS modules, the average value of the attenuation parameters of the second slices of the all WSS modules,. , and the average value of the attenuation parameters of the N-th slices of the all WSS modules are calculated in sequence, and then the first slices of the WSS modules, the second slices of the WSS modules,. , and the N-th slices of the WSS modules in the cascaded WSS system are adjusted in sequence based on the obtained averages.

The following further describes the control of the WSS channel attenuation parameter by using an example that is not intended to limit the solution of embodiments of the present invention.

This example of the present invention describes a method and system for improving the performance of long-distance <NUM>/B <NUM> quasi-Nyquist WDM transmission in a cascaded Flex ROADM system. In this long-distance transmission system, a frequency spacing between channels is close to the baud rate of traffic light. That is, quasi-Nyquist WDM transmission is implemented. For example, <NUM> PM-QPSK and <NUM> PM-16QAM traffic signals having a baud rate of about <NUM> are transmitted in a channel spacing of <NUM>, or <NUM> PM-8QAM traffic signals having a baud rate of about <NUM> are transmitted in a channel spacing of <NUM>. A service transceiver in the system uses a coherent receiver optical module. Moreover, the DSP clock synchronization algorithm at the receiving end of the optical module extracts a clock component from signal light. Penetration of cascading WSSs exist in the end-to-end transmission link of traffic light in the system. The WSSs include WSS units for optical add multiplexing, WSS units for optical drop demultiplexing and WSS units in the bypass direction of ROADM sites. The frequency adjustment granularity supported by the WSS units of the system is significantly smaller than the channel spacing. The corresponding smallest adjustable frequency gird is <NUM>, <NUM> or <NUM>.

Based on the preceding solution, this example of the present invention further provides a WSS spectrum shaping unit having adjustable attenuation within the bandwidth. This unit uses a slice attenuation control method for multiple slices (which may be understood as the slices in this embodiment) in a channel. The method includes the steps below.

In this step, after the WSS channel attenuation parameter of various slices of the channel is adjusted symmetrically about the center of the channel, the attenuation parameter of the slices at the outermost edge of the channel is zero. After the adjustment, the spectrum shape of the channel remains symmetrical, and the spectrum in segment fc - B/<NUM> to fc + B/<NUM> is approximately flat, that is, the difference between the central frequency component and the edge frequency component in the channel is relatively reduced.

In this manner, the channel shaping parameters (that is, the attenuation parameters adjusted in the preceding steps <NUM>, <NUM>, and <NUM>) of the penetrated WSS units in this traffic configuration are obtained. When traffic is established in a cascaded WSS system, it is feasible to configure the channel shaping parameters for the WSS units at optical multiplexing, optical demultiplexing and ROADM penetration points in a transmission link and perform traffic spectrum shaping for each stage of WSS unit.

Before the preceding steps are performed, when the WSS channel attenuation parameter of each slice in the channel is adjusted, wide-spectrum white noise (which may be understood as the white noise of this embodiment) is connected to the input end of each WSS unit and the output spectrum shape is monitored by a spectrum analyzer at the output end of each WSS unit. Such operation is performed for feedback adjustment of the WSS channel attenuation parameter.

In summary, in this example of the present invention, additional attenuation adjustment (for the effect, see <FIG>) of the spectral center spectral component of each WSS unit is performed using the spectrum shaping method of WSS slice attenuation control. Such operation helps reduce the difference between the central frequency component and the edge frequency component caused by WSS filtering and ensures that the clock synchronization algorithm at the receiving end effectively extracts the clock from the high-frequency component of a signal, thereby improving the reliable receptivity of the <NUM>/B100G coherent receiver after cascaded WSSs are cascaded. In addition, as shown in <FIG>, compared with the pre-emphasis spectrum shaping method of an existing optical transceiver, in this embodiment of the present invention, spectrum shaping at each WSS unit in an optical link helps suppress the filtering effect of each WSS, overcome the problem of limited WSS penetration level caused by insufficient pre-emphasis capability of the optical transceiver, and significantly improve the penetration capability of cascaded WSSs of the optical transceiver. The shaping parameter configuration of this example of the present invention ensures that each WSS uses the same shaping parameter that is not dynamically adjusted as the stage of each WSS unit in an optical link is changed, helping reducing the end-to-end link detection of traffic light at the network control level and the feedback control of the pre-emphasis parameters of an optical transceiver. Moreover, in this example of the present invention, the implementation method is simple and low in cost since it is feasible simply to perform SLICE-level software control and adjustment of units whose WSS bandwidth attenuation is adjustable and not to add additional optical devices in a transmission link.

It is to be noted that the WSS channels and channels mentioned in this embodiment and this example of the present invention may have the same meaning. For example, these channels are all WSS channels or are all channels. Of course, these channels may have different meanings. This is not limited in this embodiment of the present invention.

From the description of the preceding implementations, it will be apparent to those skilled in the art that the method of the preceding embodiment may be implemented by software plus a necessary general-purpose hardware platform or may, of course, be implemented by hardware. However, in many cases, the former is a preferred implementation. Based on this understanding, the solution of the present invention substantially, or the part contributing to the existing art, may be embodied in the form of a software product. The software product is stored in a storage medium (such as a ROM/RAM, a magnetic disk or an optical disk) and includes several instructions for enabling a terminal (which may be a mobile phone, a computer, a server or a network device) to execute the method of each embodiment of the present invention.

In this embodiment, a device for controlling the WSS channel attenuation parameter is provided. The device is configured to implement the preceding embodiment and preferred implementations. What has been described will not be repeated. As used below, the term "module" may be software, hardware or a combination thereof capable of implementing predetermined functions. The device in this embodiment is preferably implemented by software, but implementation by hardware or by a combination of software and hardware is also possible and conceived.

<FIG> is a block diagram illustrating the structure of the device for controlling the WSS channel attenuation parameter according to an embodiment of the present invention. As shown in <FIG>, the device includes an input module <NUM>, an adjustment module <NUM> and a control module <NUM>.

The input module <NUM> is configured to, for each WSS module in a cascaded WSS system, input white noise to the channel of each WSS module.

The adjustment module <NUM> is configured to adjust the attenuation parameters of all slices of the channel according to a predefined rule such that the flatness of the output spectrum of the white noise is less than a first threshold.

The control module <NUM> is configured to calculate the average value of the adjusted attenuation parameters of the slices of a plurality of WSS modules and control the WSS channel attenuation parameter of each WSS module based on the average value.

Through the application of the preceding modules, the following operations are performed for each WSS module in a cascaded WSS system: inputting white noise to the channel of each WSS module and adjusting the attenuation parameters of all slices of the channel according to a predefined rule such that the flatness of the output spectrum of the white noise is less than a first threshold; and calculating the average value of the adjusted attenuation parameters of the slices of all WSS modules and controlling the WSS channel attenuation parameter of each WSS module based on the average value. The preceding solution solves the problem in which the performance of a receiver deteriorates after filtered optical signals enter the receiver because cascaded WSSs cause filtering damage to the optical signals in the related art, thereby effectively reducing filtering damage when the optical signals pass through the cascaded WSSs and improving the performance of the receiver.

<FIG> is a block diagram illustrating the structure of the adjustment module <NUM> of the device for controlling the WSS channel attenuation parameter according to this embodiment of the present invention. As shown in <FIG>, the adjustment module <NUM> includes a first adjustment unit <NUM>, a second adjustment unit <NUM> and a third adjustment unit <NUM>.

The first adjustment unit <NUM> is configured to adjust the attenuation parameters of the secondary edge slices of all slices to obtain a first adjustment result.

The second adjustment unit <NUM> is configured to adjust the attenuation parameters of one or more center slices of the channel based on the first adjustment result to obtain a second adjustment result.

The third adjustment unit <NUM> is configured to adjust other slices of all slices excluding the secondary edge slices and the center slices based on the first adjustment result and the second adjustment result. That is, in this embodiment of the present invention, the attenuation parameters of the secondary edge slices of all slices, the attenuation parameters of the center slices of all slices and the attenuation parameters of other slices of all slices may be adjusted in sequence.

As shown in <FIG>, the first adjustment unit <NUM> is further configured to acquire the baud rate of a traffic signal of the channel; and adjust the attenuation parameters of the secondary edge slices of all slices based on the baud rate.

Optionally, the first adjustment unit <NUM> is further configured to adjust the attenuation parameters of the secondary edge slices such that the difference between the spectral height of the lowest spectral point corresponding to the secondary edge slices and the spectral height of fc - B/<NUM> is less than a second threshold or such that the difference between the spectral height of the lowest spectral point corresponding to the secondary edge slices and the spectral height of fc + B/<NUM> is less than the second threshold. fc denotes the central frequency of the channel. B denotes the baud rate of the traffic signal.

Optionally, the second adjustment unit <NUM> is further configured to match the attenuation parameters of one or more center slices of the channel with the attenuation parameters of the secondary edge slices such that the flatness of the output spectrum of the white noise in segment fc - B/<NUM> to fc or segment fc to fc - B/<NUM> is less than the first threshold.

Optionally, the third adjustment unit <NUM> is configured to adjust the attenuation parameters of other slices symmetrically by taking the central frequency fc of the channel as the central axis according to the attenuation parameters of the secondary edge slices in the first adjustment result and the attenuation parameters of the center slices in the second adjustment result.

<FIG> is a block diagram illustrating the structure of the control module <NUM> of the device for controlling the WSS channel attenuation parameter according to this embodiment of the present invention. As shown in <FIG>, the control module <NUM> includes a first processing unit <NUM> and a second processing unit <NUM>.

The first processing unit <NUM> is configured to acquire the attenuation parameters of first slices of all WSS modules separately and calculate the average value of the attenuation parameters of the first slices of the all WSS modules.

The second processing unit <NUM> is configured to acquire the attenuation parameters of second slices of the all WSS modules to the attenuation parameters of the N-th slices of the all WSS modules in sequence and calculate the average value of the attenuation parameters of the second slices of the all WSS modules to the average value of the attenuation parameters of the N-th slices of the all WSS modules.

That is, in this embodiment of the present invention, the average value of the attenuation parameters of the first slices of all WSS modules, the average value of the attenuation parameters of the second slices of all WSS modules,. , and the average value of the attenuation parameters of the N-th slices of all WSS modules are calculated in sequence, and then the first slices of the WSS modules, the second slices of the WSS modules,. , and the N-th slices of the WSS modules in the cascaded WSS system are adjusted in sequence based on the obtained averages.

It is to be noted that the preceding modules may be implemented by software or hardware. Implementation by hardware may, but not necessarily, be performed in the following manner: the preceding modules are located in the same processor or the preceding modules are located in any combination in their respective processors.

It is to be noted that the solution of embodiment one and the solution of embodiment two may be used in combination or separately. This is not limited in this embodiment of the present invention.

The following describes the process for controlling of the WSS channel attenuation parameter in conjunction with preferred embodiments that are not intended to limit the solution of embodiments of the present invention.

Preferred embodiment one of the present invention provides a method for adjusting attenuation in a WSS channel bandwidth. This method is applied to the scenario where <NUM> QPSK/<NUM> <NUM> quadrature amplitude modulation (QAM) optical signals pass through cascaded WSSs in a channel bandwidth of <NUM>. <FIG> shows the steps of adjusting the WSS channel attenuation parameter of <NUM> × <NUM> slices in the WSS channel (which may be understood as the channel mentioned in the preceding embodiments) bandwidth. The steps are described below.

In step <NUM>, wide-spectrum white noise is input to a single WSS unit, the central frequency and channel bandwidth of the WSS unit are set, the output end of the WSS unit is connected to a spectrum analyzer, the WSS channel bandwidth is set to <NUM>, and the six <NUM> slices are configured with the same WSS channel attenuation parameter. The output spectrum shape in this case is shown in <FIG>.

In step <NUM>, the central frequency fc of the output spectrum is found, and the two horizontal frequency calibration lines of the spectrum analyzer are adjusted to fc - B<NUM>/<NUM> and fc + B<NUM>/<NUM> based on the baud rate B<NUM> of a traffic transceiver module, for example, a baud rate B<NUM> of about <NUM> Gbaud of both a <NUM> PM-QPSK traffic module with <NUM>% FEC overhead and a <NUM> PM-16QAM traffic module with <NUM>% FEC overhead.

In step <NUM>, the WSS channel attenuation parameter of secondary edge slice <NUM> in the WSS channel bandwidth is adjusted such that the spectral height of the lowest spectral point f<NUM> in segment fc -B<NUM>/<NUM> to fc is close to the spectral height of fc - B<NUM>/<NUM>. The adjusted output spectrum is shown in <FIG>.

In step <NUM>, the WSS channel attenuation parameter of center slice <NUM> in the WSS channel bandwidth is adjusted such that the spectrum in segment fc - B<NUM>/<NUM> to fc is approximately flat, or more specifically, the flatness of the channel in this segment does not exceed <NUM> dB. The adjusted output spectrum is shown in <FIG>.

In step <NUM>, the WSS channel attenuation parameter of slice <NUM> and the WSS channel attenuation parameter of slice <NUM> in the WSS channel bandwidth are adjusted symmetrically about the center of the channel, that is, the WSS channel attenuation parameter of slice <NUM> and the WSS channel attenuation parameter of slice <NUM> are set to the same as the WSS channel attenuation parameter of slice <NUM> and the WSS channel attenuation parameter of slice <NUM> respectively. The adjusted WSS channel attenuation parameter of the six <NUM> slices is symmetrical about the central frequency fc. The corresponding output spectrum is also symmetrical. The adjusted output spectrum is shown in <FIG>. In this case, the attenuation adjustment parameters of the WSS unit are obtained.

In step <NUM>, in view of little difference between WSSs, N (which is not less than <NUM>) WSS modules are selected, steps <NUM> to <NUM> are performed repeatedly for the selected N modules so that the attenuation parameters of the slices of the WSS modules are acquired in sequence, the average value of the N attenuation parameters of the individual slices of the WSS modules is calculated separately, and finally the average is used as the attenuation configuration parameter of a corresponding slice in the WSS channel bandwidth.

In summary, preferred embodiment one of the present invention provides a method for shaping in a WSS channel bandwidth of <NUM>. The WSS channel attenuation parameter of each slice is adjusted according to the serial number of the each slice. It is also feasible to perform the symmetrical adjustment of step <NUM> in a different sequence. That is, it is feasible to adjust secondary slices <NUM> and <NUM> and then adjust center slices <NUM> and <NUM> as long as the obtained channel attenuation parameters are the same in the two adjustment sequences. This method for shaping in a WSS channel bandwidth of <NUM> is applied to the penetration scenario where <NUM> QPSK/<NUM> 16QAM signals pass through cascaded WSSs. When this type of traffic is initiated, the system configures the WSS channel attenuation parameter for the six <NUM> slices of the WSS unit in the <NUM> channel bandwidth. Based on a spectrum shaping method for attenuation control in a WSS bandwidth, the method of this preferred embodiment suppresses the difference between the central frequency component and the edge frequency component caused by filtering of cascaded WSSs and ensures that the clock synchronization algorithm at the receiving end effectively extracts the clock component, thereby improving the receptivity of an optical transceiver.

Preferred embodiment two of the present invention provides a method for adjusting attenuation in a WSS channel bandwidth. This method is applied to the scenario where <NUM> PM-8QAM optical signals pass through cascaded WSSs in a channel bandwidth of <NUM>. The steps of adjusting the WSS channel attenuation parameter of <NUM> × <NUM> slices in the WSS channel bandwidth are described below.

In step <NUM>, wide-spectrum white noise is input to a single WSS unit, the central frequency and channel bandwidth of the WSS unit are set, the output end of the WSS unit is connected to a spectrum analyzer, the WSS channel bandwidth is set to <NUM>, and the eight slices are configured with the same WSS channel attenuation parameter. For ease of description, it is assumed that the eight slices in the <NUM> WSS channel bandwidth are numbered <NUM> to <NUM> in sequence.

In step <NUM>, the central frequency fc of the output spectrum is found, and the two horizontal frequency calibration lines of the spectrum analyzer are adjusted to fc - B<NUM>/<NUM> and fc + B<NUM>/<NUM> based on the baud rate B<NUM> of a traffic transceiver module, for example, a baud rate B<NUM> of about <NUM> Gbaud of a <NUM> PM-8QAM traffic module with <NUM>% FEC overhead.

In step <NUM>, the WSS channel attenuation parameter of secondary edge slice <NUM> in the WSS channel bandwidth is adjusted such that the spectral height of the lowest spectral point in segment fc -B<NUM>/<NUM> to fc is close to the spectral height of fc - B<NUM>/<NUM>.

In step <NUM>, the WSS channel attenuation parameter of center slices <NUM> and <NUM> in the WSS channel bandwidth is adjusted and the same adjustment is made to attenuation of two slices in the center such that the spectrum in segment fc - B<NUM>/<NUM> to fc is approximately flat, or more specifically, the flatness of the channel in this segment does not exceed <NUM> dB.

In step <NUM>, the WSS channel attenuation parameter of slices <NUM>, <NUM> and <NUM> in the channel bandwidth is adjusted symmetrically about the center of the channel. The adjusted WSS channel attenuation parameter of the eight slices is symmetrical about the central frequency fc. In this case, the attenuation adjustment parameters of the WSS unit are obtained.

In step <NUM>, N WSS modules are selected, the attenuation parameters of the slices of the WSS modules are acquired in sequence, the average value of the N attenuation parameters of the individual slices of the WSS modules is calculated separately, and the average is used as the attenuation configuration amount of a corresponding slice in the WSS channel bandwidth.

In summary, this preferred embodiment of the present invention provides a method for shaping in a WSS channel bandwidth of <NUM>. The WSS channel attenuation parameter of each slice is adjusted according to the serial number of the each slice. It is also feasible to perform the symmetrical adjustment of step <NUM> in a different sequence. That is, it is feasible to adjust secondary slices <NUM> and <NUM> and then adjust center slices <NUM> to <NUM> as long as the obtained channel attenuation parameters are the same in the two adjustment sequences. This method for shaping in a WSS channel bandwidth of <NUM> is applied to the penetration scenario where <NUM> 8QAM signals pass through cascaded WSSs. When this type of traffic is initiated, the system configures the WSS channel attenuation parameter for the eight <NUM> slices of the WSS unit in the <NUM> channel bandwidth. Based on a spectrum shaping method for attenuation control in a WSS bandwidth, the method of this preferred embodiment improves the receptivity of an optical transceiver in a cascaded WSS system.

Preferred embodiment three of the present invention provides a method for adjusting attenuation in a WSS channel bandwidth. This method is applied to the scenario where <NUM> PM-QPSK optical signals pass through cascaded WSSs in a channel bandwidth of <NUM>. The steps of adjusting the WSS channel attenuation parameter of <NUM> × <NUM> slices in the WSS channel bandwidth are described below.

In step <NUM>, wide-spectrum white noise is input to a single WSS unit, the central frequency and channel bandwidth of the WSS unit are set, the output end of the WSS unit is connected to a spectrum analyzer, the WSS channel bandwidth is set to <NUM>, and the <NUM> slices are configured with the same WSS channel attenuation parameter. For ease of description, it is assumed that the <NUM> slices in the <NUM> WSS channel bandwidth are numbered <NUM> to <NUM> in sequence.

In step <NUM>, the central frequency fc of the output spectrum is found, and the two horizontal frequency calibration lines of the spectrum analyzer are adjusted to fc - B<NUM>/<NUM> and fc + B3/<NUM> based on the baud rate B<NUM> of a traffic transceiver module, for example, a baud rate B<NUM> of about <NUM> Gbaud of a <NUM> PM-QPSK traffic module with <NUM>% FEC overhead.

In step <NUM>, the WSS channel attenuation parameter of center slices <NUM>, <NUM>, <NUM> and <NUM> in the WSS channel bandwidth is adjusted and the same adjustment is made to attenuation of four slices in the center such that the spectrum in segment fc - B<NUM>/<NUM> to fc is approximately flat, or more specifically, the flatness of the channel in this segment does not exceed <NUM> dB.

In step <NUM>, the WSS channel attenuation parameter of slices <NUM>, <NUM>, <NUM>, <NUM> and <NUM> in the channel bandwidth is adjusted symmetrically about the center of the channel. The adjusted WSS channel attenuation parameter of the <NUM> slices is symmetrical about the central frequency fc. In this case, the attenuation adjustment parameters of the WSS unit are obtained.

In step <NUM>, N WSS modules are selected, the attenuation parameters of the slices of the WSS modules are acquired in sequence, the average value of the N attenuation parameters of the individual slices of the WSS modules is calculated separately, and the average is used as the attenuation configuration parameter of a corresponding slice in the WSS channel bandwidth.

In summary, preferred embodiment three of the present invention provides a method for shaping in a WSS channel bandwidth of <NUM>. The WSS channel attenuation parameter of each slice is adjusted according to the serial number of the each slice. It is also feasible to perform the symmetrical adjustment of step <NUM> in a different sequence. That is, it is feasible to adjust secondary slices <NUM> and <NUM> and then adjust center slices <NUM> to <NUM> as long as the obtained channel attenuation parameters are the same in the two adjustment sequences. This method for shaping in a WSS channel bandwidth of <NUM> is applied to the penetration scenario where <NUM> PM-QPSK signals pass through cascaded WSSs. When this type of traffic is initiated, the system configures the WSS channel attenuation parameter for the <NUM><NUM> slices of the WSS unit in the <NUM> channel bandwidth. Based on a spectrum shaping method for attenuation control in a WSS bandwidth, the method of this preferred embodiment improves the receptivity of an optical transceiver in a cascaded WSS system.

Preferred embodiment four of the present invention provides a filtering performance optimization method based on WSS slice control. This WSS slice control method uses a finer spectral granularity. For example, the minimum adjustable spectral granularity is <NUM>. Based on the preceding three preferred embodiments, this method further improves the spectral flatness and the receptivity of an optical transceiver after cascaded WSSs are cascaded. The steps of adjusting the WSS channel attenuation parameter of <NUM> × <NUM> slices in the WSS channel bandwidth are described below by using <NUM> PM-QPSK as an example.

In step <NUM>, the central frequency fc of the output spectrum is found, and the two horizontal frequency calibration lines of the spectrum analyzer are adjusted to fc - B<NUM>/<NUM> and fc + B<NUM>/<NUM> based on the baud rate B<NUM> of a traffic transceiver module.

In summary, preferred embodiment four of the present invention provides a method for shaping in a WSS channel bandwidth of <NUM>. The WSS channel attenuation parameter of each slice is adjusted according to the serial number of the each slice. It is also feasible to perform the symmetrical adjustment of step <NUM> in a different sequence. That is, it is feasible to adjust secondary slices <NUM> and <NUM> and then adjust center slices <NUM> to <NUM> as long as the obtained channel attenuation parameters are the same in the two adjustment sequences. This method for shaping in a WSS channel bandwidth of <NUM> is applied to the penetration scenario where <NUM> PM-QPSK signals pass through cascaded WSSs. When this type of traffic is initiated, the system configures the WSS channel attenuation parameter for the <NUM><NUM> slices of the WSS unit in the <NUM> channel bandwidth. For several other traffic types having bandwidths with different baud rates, the number of adjustable slices in a bandwidth varies with the traffic type corresponding to the bandwidth. The method involved is the same as described earlier and will not be repeated here. This spectrum shaping method based on WSS with a finer adjustable spectral granularity improves the flatness of a WSS channel and thereby further improves the receptivity of an optical transceiver in a cascaded WSS system.

An embodiment of the present invention provides a storage medium. The storage medium includes a stored program. When the program is executed, the method of any one of the preceding embodiments is performed.

Optionally, in this embodiment, the storage medium may be configured to store program codes for performing the steps below.

In S1, for each WSS module in a cascaded WSS system, white noise is input to the channel of each WSS module and the attenuation parameters of all slices of the channel are adjusted according to a predefined rule such that the flatness of the output spectrum of the white noise is less than a first threshold.

In S2, the average value of the adjusted attenuation parameters of the slices of a plurality of WSS modules is calculated and the WSS channel attenuation parameter of each WSS module is controlled based on the average value.

Optionally, the storage medium is further configured to store program codes for performing the steps below.

In S3, the attenuation parameters of the secondary edge slices of all slices are adjusted so that a first adjustment result is obtained.

In S4, the attenuation parameters of one or more center slices of the channel are adjusted based on the first adjustment result so that a second adjustment result is obtained.

In S5, other slices of all slices than the secondary edge slices and the center slices are adjusted based on the first adjustment result and the second adjustment result.

Optionally, in this embodiment, the storage medium may include, but is not limited to, a U disk, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk, an optical disk or another medium capable of storing program codes.

Optionally, for specific examples in this embodiment, reference may be made to the examples described in the preceding embodiments and optional implementations, and the specific examples will not be repeated in this embodiment.

Apparently, it is to be understood by those skilled in the art that the modules or steps in embodiments of the present invention may be implemented by a general-purpose computing device and may be concentrated on a single computing device or distributed in a network formed by multiple computing devices. Optionally, these modules or steps may be implemented by program codes executable by the computing device. Thus, these modules or steps may be stored in a storage device and executed by the computing device. Moreover, in some cases, the illustrated or described steps may be executed in a sequence different from the sequence described herein. Alternatively, each module or step may be implemented by being made into an integrated circuit module separately or multiple ones of these modules or steps may be implemented by being made into a single integrated circuit module. In this manner, the present invention is not limited to any specific combination of hardware and software.

The preceding are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations.

Claim 1:
A method for controlling a wavelength-selective switch, WSS, channel attenuation parameter, comprising:
for each WSS module in a cascaded WSS system, inputting (S302) white noise to a WSS channel of the each WSS module and adjusting attenuation parameters of all N slices of the WSS channel according to a predefined rule until a flatness of an output spectrum of the white noise being less than a first threshold; and
calculating (S304) an average value of adjusted attenuation parameters of slices of WSS channels of a plurality of WSS modules and controlling an WSS channel attenuation parameter of the each WSS module based on the average value;
wherein the adjusting the attenuation parameters of all N slices of the WSS channel according to the predefined rule comprises:
adjusting attenuation parameters of secondary edge slices of the N slices to obtain a first adjustment result;
adjusting attenuation parameters of one or more center slices of the WSS channel based on the first adjustment result to obtain a second adjustment result; and
adjusting other slices of the N slices excluding the secondary edge slices and the one or more center slices based on the first adjustment result and the second adjustment result;
wherein the secondary edge slices are slices next to the slice of the left spectrum edge or the right spectrum edge, the other slices refer to slices in which the secondary edge slices and the one or more center slices are excluded from the N slices, and N is an integer greater than <NUM>;
characterized in that, the adjusting the attenuation parameters of the secondary edge slices of the N slices comprises:
acquiring a baud rate of a traffic signal of the channel; and
adjusting the attenuation parameters of the secondary edge slices of the N slices based on the baud rate.