KR20130118803A - Wavelength tuning time measurement apparatus and method for the multi-wavelengths passive optical network - Google Patents

Abstract

PURPOSE: A wavelength tuning time measurement apparatus and method for multi-wavelength passive optical network (MW PON) are provided to select a wavelength-variable light source considering the required wavelength tuning time of an MW PON system. CONSTITUTION: A wavelength-variable light source (100) comprises a wavelength-variable laser (110) and a wavelength-variable laser driving unit (120). The wavelength-variable laser generates various wavelengths of light. The wavelength-variable laser driving unit includes information about the wavelength of light generated by the wavelength-variable laser in a wavelength change signal and transmits the wavelength change signal to the wavelength-variable laser. If the wavelength-variable laser receives the wavelength change signal from the wavelength-variable laser driving unit, the wavelength-variable laser generates a predetermined wavelength of light. A wavelength tuning time measuring device (200) measures the wavelength tuning time of the wavelength-variable light source. An optical filter (210) passes only a predetermined wavelength of light, for example, light within a channel wavelength range. An optical detector (220) generates information about time when the light passing through the optical filter consecutively begins to reach or calculates a wavelength tuning time by using the information. [Reference numerals] (110) Wavelength-variable laser; (120) Wavelength-variable laser driving unit; (210) Optical filter; (220) Optical detector; (300) Attenuator

Description

Wavelength tuning time measurement apparatus and method for the multi-wavelengths passive optical network

The present invention relates to a passive optical network (PON), and more particularly to an apparatus and method for measuring wavelength tuning time in a multi-wavelength passive optical network (MW PON).

Due to the development of optical communication technology and the rapid increase of internet service demand, basic research on optical subscriber network has been conducted since the early 2000s. The introduction of broadband subscriber networks, such as To The Home and Fiber To The Office, has become commonplace. In addition, the explosion of mobile IP terminals such as smart phones and tablet computers, the commercialization of IPTV services, and the expansion of multimedia broadcasting / streaming services through the Internet, etc. In order to cope with the increase in traffic, the research on the next generation ultra high-speed high-capacity optical subscriber network technology has been actively conducted.

In order to efficiently provide services to more subscribers with limited network resources, Time Division Multiplexing (TDM) and Wavelength Division Multiplexing (WDM) techniques are applied to optical subscriber network technology. have. Recently, researches on the optical subscriber network to which the hybrid technique in which the TDM technique and the WDM technique are applied are being conducted. Attempts have also been made to integrate orthogonal frequency division multiplexing (OFDM) techniques, which are currently used in wireless communications, with optical network technology, which is an example of a hybrid technique in a broad sense.

In the WDM system or the hybrid system, communication can be performed using a plurality of wavelength bands, i.e., multiple wavelengths. As the use of the Internet increases and the demand for multimedia contents explosively increases, it is an important problem to increase the bandwidth of the network in both wired optical subscriber network and wireless network or both wired and wireless networks. Is attracting attention as a way to solve this problem. Accordingly, it is possible not only to provide a high-speed communication service to a large number of subscribers, but also to facilitate communication capacity and expansion of subscribers, and excellent communication security. Therefore, the multi-wavelength passive optical network (MW PON) employing the WDM scheme or the hybrid scheme is attracting great attention in the next generation high-speed, high-capacity optical network system.

The multi-wavelength passive optical network (MW PON) system includes a service provider apparatus (hereinafter, also referred to as an OLT) located at the central office (CO) side, a plurality of subscribers (Hereinafter also referred to as " ONUs ") and one or more optical multiplexers / demultiplexers or optical intensity splitters, Or an optical distribution unit (ODN)). In such an MW PON system, the network configuration may be changed depending on the type of the light source used, for example, a spectrum-divided light source, a wavelength-locked light source, or a wavelength independent light source. And the wavelength of light used in the MW PON system can be fixed or variable between the OLT and the particular ONU.

In a WDM PON or a hybrid PON using a multi-wavelength passive optical communication network such as a wavelength multiplexing scheme, active researches are being made on the use of a wavelength variable light source to efficiently utilize wavelength resources. The use of a tunable light source solves problems that may result from producing, installing, and managing light sources for each wavelength. In addition, efficient and user-friendly services are possible, such as dynamically assigning wavelengths to achieve load balancing, or when a link is switched, quickly changing to another wavelength to set up a new link.

Communication between the OLT and each ONU using a tunable light source requires a tunable process or a wavelength tuning process in which the tunable light source stably generates light having a wavelength different from that of the original wavelength. In addition, the wavelength tuning time may vary according to a mechanism of changing wavelengths or wavelength spacing between channels to be changed in the wavelength tuning process in the MW PON system. Therefore, the wavelength tuning time of the tunable light source should be considered mainly in the procedure for establishing a link to the new wavelength between the OLT and the ONU. In particular, in view of the MW PON system in which the ODN is provided with a light intensity divider instead of a wavelength-specific MUX, when the wavelength tuning time of the variable wavelength light source is not sufficiently considered, the variable wavelength light source is not completed properly. It can be operated to affect channels of different wavelengths. Therefore, there is a need for an apparatus and procedure for clearly defining the wavelength tuning time of a tunable light source and accordingly measuring the wavelength tuning time.

One object of the present invention is to provide a wavelength tuning time measuring apparatus and method for measuring the wavelength variable time of the variable wavelength light source when the output wavelength of the variable wavelength light source provided in the multi-wavelength passive optical communication network is to be changed. To provide.

A wavelength tuning time measuring apparatus according to an embodiment of the present invention for solving the above problems is a wavelength tuning time measuring apparatus for measuring the wavelength tuning time of a wavelength variable light source provided in a multi-wavelength passive optical communication network (MW PON) system And a light filter for passing only light having a predetermined wavelength bandwidth, and a light detector for detecting light passing through the light filter, wherein the wavelength tuning time is from a time when a wavelength change signal is transmitted to the wavelength variable light source. It may be a time taken until the light detector continuously starts to sense light. The center of the predetermined wavelength bandwidth may be aligned with the center wavelength in the ITU-T channel grid.

According to one aspect of the embodiment, the transmission bandwidth of the optical filter may correspond to a channel wavelength range, which is a wavelength range required to operate at the performance required for the MW PON system.

According to another aspect of the embodiment, the transmission bandwidth of the optical filter may correspond to a channel frequency range, which is a frequency range required to operate at the performance required by the MW PON system.

According to another aspect of the embodiment, the transmission bandwidth of the optical filter may correspond to a maximum spectral excursion.

According to another aspect of the embodiment, the optical filter may be a multilayer thin film filter, chirped optical waveguide Bragg grating filter, chirped fiber Bragg grating filter, or AWG (Arrayed Waveguide Gating) filter.

According to another aspect of the embodiment, the center wavelength of the optical filter may match the ITU-T channel grid. The center wavelength of the optical filter may be changed.

According to another aspect of the embodiment, the wavelength tuning time may be utilized in a link establishment procedure or a link change procedure between a service provider device and a subscriber device of the MW PON system. For example, it may be used to move to a newly allocated wavelength channel during or after the activation of the ONU of the MW PON system. As another example, in an MW PON system including a plurality of OLTs, in order to operate some OLTs in the power save mode, the operation is stopped and the ONUs connected to the wavelength channels are moved to communicate with other OLTs in operation. May be utilized. In another example, the MW PON system may be used to dynamically allocate wavelength resources, or may be used to determine performance such as whether the output wavelength of a tunable light source drifts or is well maintained within a predetermined grid. Can be.

The wavelength tuning time measuring method according to an embodiment of the present invention for solving the above problems is a wavelength tuning time measuring method for measuring the wavelength tuning time of a wavelength variable light source provided in a multi-wavelength passive optical communication network (MW PON) system Changing the wavelength of light generated from the variable wavelength light source, sensing light passing through an optical filter for passing only light having a predetermined wavelength bandwidth, and from a time when a wavelength changing signal is transmitted to the variable wavelength light source And calculating the wavelength tuning time as the time taken until the light starts to be continuously detected in the sensing step. The center of the predetermined wavelength bandwidth may be aligned with the ITU-T channel grid.

According to one aspect of the embodiment, the transmission bandwidth of the optical filter may correspond to a channel wavelength range, which is a wavelength range required to operate at the performance required for the MW PON system.

According to another aspect of the embodiment, the transmission bandwidth of the optical filter may correspond to a channel frequency range, which is a frequency range required to operate at the performance required by the MW PON system.

According to another aspect of the embodiment, the transmission bandwidth of the optical filter may correspond to a maximum spectral excursion.

According to another aspect of the embodiment, the optical filter may be a multilayer thin film filter, chirped optical waveguide Bragg grating filter, chirped fiber Bragg grating filter, or AWG (Arrayed Waveguide Gating) filter.

According to another aspect of the embodiment, the center wavelength of the optical filter may match the ITU-T channel grid. The center wavelength of the optical filter may be changed.

According to another aspect of the embodiment, the wavelength tuning time may be utilized in a link establishment procedure or a link change procedure between a service provider device and a subscriber device of the MW PON system. For example, it may be utilized when moving to a newly allocated wavelength channel during or after activating ONU of the MW PON system. As another example, in an MW PON system including a plurality of OLTs, in order to operate some OLTs in the power save mode, the operation is stopped and the ONUs connected to the wavelength channels are moved to communicate with other OLTs in operation. May be utilized. In another example, the MW PON system may be used to dynamically allocate wavelength resources, or may be used to determine performance such as whether the output wavelength of a tunable light source drifts or is well maintained within a predetermined grid. Can be.

According to another aspect of the embodiment, before changing the wavelength of the variable wavelength light source may further comprise checking whether the center wavelength of the optical filter is aligned with the center wavelength of the target channel to be changed. .

According to an embodiment of the present invention, it is possible to measure the wavelength tuning time of the variable wavelength light source provided in the multi-wavelength passive optical communication network (MW PON), by using this in consideration of the required wavelength tuning time of the MW PON system The light source can be selected. In particular, using the wavelength tuning time measuring apparatus or method according to the practical example of the present invention, the MW PON system can not only affect the channel of the other wavelength when changing the wavelength of the tunable light source, but also the wavelength of the tunable light source. After the change is completely completed, communication can be made between the ONU and the OLT.

1A is a block diagram illustrating an example of a multi-wavelength passive optical communication network system including a tunable light source.
1B is a block diagram illustrating another example of a multi-wavelength passive optical communication network system including a tunable light source.
FIG. 2 is a block diagram showing an example of the configuration of a tunable light source and a wavelength tuning time measuring apparatus thereof provided in an MW PON system.
3 is a view for explaining a principle of measuring the wavelength tuning time in the wavelength tuning time measuring apparatus of FIG.
4 is a view for explaining another principle of measuring the wavelength tuning time in the wavelength tuning time measuring apparatus of FIG.
5 is a flowchart illustrating a method of measuring a wavelength tuning time of a tunable light source included in an MW PON system according to an exemplary embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The terms used are terms selected in consideration of the functions in the embodiments, and the meaning of the terms may vary depending on the user, the intention or custom of the operator, and the like. Therefore, the meaning of the terms used in the following embodiments is defined according to the definition when specifically defined in this specification, and unless otherwise defined, it should be interpreted in a sense generally recognized by those skilled in the art.

The wavelength tuning time measuring apparatus or method according to an embodiment of the present invention described below may be applied to measure the wavelength variable time or the wavelength tuning time of a variable wavelength light source used in a multi-wavelength passive optical communication network (MW PON) system. A variable wavelength light source is a light source capable of generating light of different wavelengths, and is used in a wavelength division multiplexed passive optical communication network (WDM PON) system as well as a hybrid PON in which a TDM technique and a WDM technique are combined, such as a TWDM PON or OFDM PON system. Can be used. The wavelength tuning time in the MW PON system means that when the variable wavelength light source changes the wavelength of existing light and starts to generate light of another wavelength, the light generated by the variable wavelength light source is stabilized and the wavelength within the desired range is stabilized. This means the time it takes to. Here, the wavelength within the desired range may be a wavelength range in which the center wavelength is matched to the ITU-T channel grid.

Changing the wavelength of a tunable light source in an MW PON system may be required in many cases. For example, when moving to a newly allocated wavelength channel during or after activating the ONU of the MW PON system, a wavelength change of the tunable light source may be necessary. As another example, in an MW PON system including a plurality of OLTs, in order to operate some OLTs in the power save mode, the operation is stopped and the ONUs connected to the wavelength channels are moved to communicate with other OLTs in operation. It may be necessary to change the wavelength of the tunable light source. In another example, the MW PON system may be configured to dynamically allocate wavelength resources, or may be used to determine performance such as whether the output wavelength of the variable wavelength light source drifts or is well maintained within a predetermined grid. Wavelength change may be necessary.

The wavelength tunable process in the MW PON system can be subdivided into the following processes. For example, the variable wavelength light source of the ONU may include receiving a wavelength variable command from the OLT using a PLOAM or OMCI channel, performing a wavelength change, and performing a subsequent procedure scheduled after the wavelength change is completed. .

The wavelength tuning operation of the tunable light source may occur in various cases, although it may vary depending on the type or configuration of the multi-wavelength passive optical communication network (MW PON). For example, an ONU (more specifically, a tunable light source included in the ONU) newly activated in the activation process of the ONU may require wavelength tuning to a predetermined wavelength. Even after the ONU is activated, even if the existing assigned wavelength is changed to another wavelength, the ONU may need to tune to the newly allocated wavelength. The change in the assigned wavelength may be performed by an administrator of the network system for managing wavelength resources or for performance improvement through load balancing of the network system, but is not limited thereto. .

A multi-wavelength passive optical communication network (MW PON) having such a tunable light source can be used for various types of networks as well as existing optical communication networks. One example is the backbone network for separate wireless base stations. In the separate wireless base station, a wireless controller (Remote Controller, REC) and a wireless equipment (Remote End, RE) are separated from each other. The radio equipment control station (REC) performs digital baseband signal processing and radio base station control and management, and the radio equipment (RE) transmits analog and radio RF signals such as filtering, modulation, frequency conversion and amplification through an antenna. Send and receive In addition, the separate wireless base station can operate the cell efficiently by placing only the radio equipment (RE) in the cell and the radio equipment control station (REC) in the central office. In addition, one or more radio equipment control stations (RECs) and a plurality of radio equipments (REs) may be configured in a multi-wavelength passive optical communication network (MW PON). Hereinafter, the architecture of such a multi-wavelength passive optical communication network (MW PON) will be briefly described.

FIG. 1A is a block diagram illustrating an example of a multi-wavelength passive optical communication network (MW PON) system having a variable wavelength light source, and FIG. 1B is a block diagram illustrating another example of a multi-wavelength passive optical communication network (MW PON) system. . 1A and 1B, there is a difference in whether the number of service provider apparatuses such as the OLT 10 is one (FIG. 1A) or plural (FIG. 1B) And a WDM unit 12 connected to the OLT 10 of FIG. In addition, each of the OLT 10 and the ONU 30, which is a subscriber device, may be provided with variable wavelength light sources 11 and 31. In FIG. 1A and FIG.

The MW PON system shown in FIGS. 1A and 1B is a WDM PON system in which a plurality of subscriber units, that is, an ONU 30 does not share wavelengths, or a plurality of TDM PON systems are stacked in one OLT, May be a system that is assigned a different wavelength or may be a TDM PON system stacked by wavelength that can support traffic load balancing with dynamic wavelength tuning. Alternatively, the MW PON system may be a hybrid PON system combining all or some of the characteristics of the system described above. Such an MW PON system may classify the ONU into any one of a plurality of classes based on the tunability and / or tuning speed of wavelength of the ONU.

1A and 1B, an MW PON system includes an OLT 10, an ODN 20, and an ONU 30. The OLT 10 corresponds to a service provider device, the ODN 20 corresponds to a local node or an optical distribution network, and the ONU 30 corresponds to a subscriber device. One or more OLTs 10 are located on the central base station (CO) side to transmit downlink data λ _a , λ _{a + 1} ,..., Λ _{a + n} from each of the plurality of ONUs 30 Uplink data λ _b , λ _{b + 1} ,..., Λ _{b + m} are received from each of the ONUs 30.

The ONU 10 and the OLT 30 of the MW PON system include the variable wavelength light sources 11 and 31, respectively. For example, the tunable light sources 11, 31 may be in the OLT 10 and / or each of the plurality of ONUs 30. There is no particular limitation on the type of the tunable light source in this embodiment, and the type of the tunable light source may vary according to the type of the MW PON system. Using a variable wavelength light source not only solves the problems associated with producing, installing, and managing light sources for each wavelength, but also dynamically allocates wavelengths to achieve load balancing or when a link of a particular wavelength is congested. Can be changed quickly to ensure smooth communication.

Each of the plurality of ONUs 30 exchanges downlink data and uplink data with the OLT 10 using the assigned unique wavelength. At this time, depending on the type of the MW PON system, the ONU 30 may transmit data only within the allocated transmission time, but the present embodiment is not limited thereto.

The ODN 20 includes one or more splitters or optical multiplexer / demultiplexers (WDM mux / demux) to separate / demultiplex the downstream transmitted from the OLT 10 for each ONU. (30_1, 30_2, ..., 30_k) or upstream received from each ONU (30_1, 30_2, ..., 30_k) to combine / multiplexed to the OLT (10). Depending on the number of splitters or optical multiplexers / demultiplexers, the process of combining / multiplexing and separating / demultiplexing may be composed of a plurality of stages. In FIG. 1A and FIG. 1B, reference numeral IF _PON denotes an interface of a passive optical communication network, and in this embodiment, there is no particular limitation.

In order to send and receive data between one or more OLT 10 and each of a plurality of ONUs 30 in the MW PON system as shown in Figs. 1A and 1B, the OLT 10 and each ONU 30_1, 30_2, ..., , ≪ / RTI > 30_k). The process of establishing a link may use a PLOAM or OMCI channel. If the process of establishing a link is broken down, each ONU 30_1, 30_2,…, 30_k initializes its own wavelength, and the OLT 10 In other words, it may be divided into a process of allocating a wavelength to be used by each ONU 30_1, 30_2,..., 30_k. The link setting process in the MW PON system including the tunable light sources 11 and 31 also includes a wavelength tuning process (time required) of the tunable light sources 11 and 31.

In the MW PON system including the splitter-based ODN 20, the ONU (e.g., the ONU 30 - k) newly installed in the system can operate only after being assigned an initial wavelength. The initial wavelength may include a wavelength for downstream and a wavelength for upstream. The assignment procedure of the initial wavelength, that is, the wavelength initialization procedure is essential for the activation of each ONU 30_k. When the new ONU 30_k is installed in the ODN 20, the initial downstream wavelength and the upstream wavelength are automatically and constantly spaced between the OLT 10 and the new ONU 30_k Should be assigned. This wavelength allocation process can be executed as a part of the activation of the new ONU 30_k. In order for the new ONU 30_k to properly communicate with the OLT 10, the downstream wavelength and the upstream wavelength for this new ONU 30_k should be specified as soon as possible and wavelength tuning may be required during the activation. In the MW PON system including the AWG (Arrayed Waveguide Gating) -based ODN 20, in the ODN 20 from the OLT 10 to the ONU 30 or from the ONU 30 to the OLT 10, Only can pass. In this case, wavelength assignment may be made during the physical installation process.

If some wavelengths in the MW PON system are idle in case of low or heavy traffic and other wavelengths are heavily loaded, the ONUs of all or some of the ONUs to which the loaded wavelengths are assigned are switched to the idle wavelength May be an example of changing the wavelength assigned to the ONU. This can balance traffic between the available wavelengths and keep the PON operation stable. Alternatively, if most of the wavelengths are used in the MW PON system, but the traffic is small at each wavelength, the MW PON system may be efficiently operated by reducing the wavelength used. In this case, an arbitrary port of the OLT can be turned off and the ONU can be changed into a subset of the available wavelength, thereby saving power of the OLT.

In the MW PON system, the link setting or resetting process includes a wavelength tuning process, which is a process until the OLT or ONU having the variable wavelength light source generates light and stably emits light at a predetermined wavelength. The wavelength tuning or wavelength tunability of the tunable light source includes not only oscillating light of the wavelength allocated to the ONU in the link setup process in the MW PON system but also changing the wavelength of light oscillated at the newly allocated wavelength. To this end, the ONU and / or OLT of the MW PON system may be equipped with a tunable light source or a tunable optical transceiver (OTRx).

However, in the wavelength tuning process, the wavelength tuning time may vary depending on the type, characteristics, and grade of the tunable light source. Therefore, in the process of establishing a link between the OLT and the ONU, the wavelength tuning time of the tunable light source included in the corresponding MW PON system should be considered. That is, the wavelength tunable laser to be used in the MW PON system where the wavelength is frequently changed due to wavelength dynamic allocation, etc., may be a very important performance parameter. For example, the MW PON system may be classified into a plurality of classes according to the wavelength tuning speed or the wavelength tuning time. Since the wavelength tuning time may vary depending on the measuring method, a uniform method for measuring the wavelength tuning time and a device implementing the same are required for the tunable light source. The wavelength tuning time of the tunable light source must satisfy the time required by the MW PON system.

FIG. 2 is a block diagram showing an example of a configuration of a wavelength tunable light source included in the MW PON system of FIG. 1A or 1B and a configuration of a wavelength tuning time measuring device of the tunable light source according to an embodiment of the present invention. In FIG. 2, reference numeral 100 corresponds to a variable wavelength light source, reference numeral 200 corresponds to a wavelength tuning time measuring apparatus, and reference numeral 300 corresponds to an attenuator. Among these, the attenuator 300 is an optional component, which is to prevent the overload of the light detector of the wavelength tuning time measuring apparatus 200 by reducing its size when the light intensity of the tunable light source 100 is too large. . 3 and 4 are diagrams for explaining the principle of measuring the wavelength tuning time in the wavelength tuning time measuring apparatus 200 of FIG.

Referring to FIG. 2, the wavelength variable light source 100 may include a wavelength variable laser 110 and a wavelength variable laser driving unit 120.

The wavelength tunable laser 110 is a means capable of generating light of a wide range of wavelengths (or frequencies), and there is no particular limitation on the type thereof in this embodiment. The tunable laser 110 may generate light of a predetermined wavelength (or frequency) within a range required for an MW PON system (see FIG. 1A or 1B) equipped with at least the tunable light sources 11 and 31. In addition, the wavelength tunable laser 110 may generate light of a predetermined wavelength (or frequency) or change the wavelength (or frequency) of light previously generated according to the control of the tunable laser driver 120. .

The wavelength tunable laser driver 120 is a means for driving the tunable laser 110, and there is no particular limitation on the specific configuration thereof. The tunable laser driver 120 may include information on the wavelength (or frequency) of the light to be generated by the tunable laser 110 in the wavelength (or frequency) change signal and transmit the information to the tunable laser 110. When the wavelength tunable laser 110 receives the wavelength change signal from the tunable laser driver 120, the wavelength tunable laser 110 may generate light having a predetermined wavelength according to the wavelength information included in the signal. If a wavelength (or frequency) change signal including wavelength (or frequency) information indicating the second wavelength (or frequency) is received while generating light at the first wavelength (or frequency), the wavelength tunable laser is received. 110 may change the wavelength (or frequency) of the generated light from the first wavelength (or frequency) to the second wavelength (or frequency).

The wavelength tuning time measuring device 200 is a device for measuring the wavelength tuning time of the wavelength variable light source 100. The wavelength tuning time refers to the time required for the wavelength of light output from the variable wavelength light source 100 to enter within a predetermined bandwidth range and stabilize from a time when a light generation command or a wavelength switch command is present. . Here, the predetermined bandwidth range may mean a channel wavelength range. This channel wavelength range corresponds to each channel of the MW PON system and its value may be determined according to the requirements of the MW PON system. The wavelength tuning time measuring apparatus 200 may include an optical filter 210 and a photo detector 220.

The optical filter 210 is for passing only light of a predetermined bandwidth, that is, light of a channel wavelength range. Light of a predetermined bandwidth refers to light whose center wavelength coincides with a particular ITU-T channel grid. The channel wavelength range, which is the transmission bandwidth of the optical filter 210, corresponds to a wavelength range that falls within a maximum acceptable difference around a nominal central frequency of the channel, and the maximum spectrum excursion. (maximum spectral excursion). Maximum spectral excursion refers to the range from (nominal center frequency to maximum allowable difference) to (nominal center frequency + maximum allowable difference). According to this, the optical filter 210 is a means for passing the light in the range of the maximum spectrum excursion. Alternatively, the transmission bandwidth of the optical filter 210 may correspond to a channel frequency range, which is a frequency range required to operate at the performance required by the MW PON system.

The optical filter 210 may be a multilayer thin film filter, a chirped optical waveguide Bragg grating filter, a chirped fiber Bragg grating filter, or an AWG (Arrayed Waveguide Gating) filter. The center wavelength of c) may match the ITU-T channel grid, which may be varied.

The photo detector 220 is a means for detecting the light passing through the optical filter 210. That is, only the light passing through the optical filter 210 reaches the photo detector 220 among the light generated by the variable wavelength light source 110, and the photo detector 220 detects the light reaching through the optical filter 210. do. There is no particular limitation on the specific type of the photodetector 220, and any means capable of detecting whether light is received regardless of the wavelength is sufficient.

In this case, the photo detector 220 may generate information about a time at which the light passing through the optical filter 210 starts to reach continuously, or calculate the wavelength tuning time using the information. That is, although the light detector 220 receives light intermittently or temporarily after a wavelength change command, it is not utilized for the calculation of the wavelength tuning time, which is because the light generated from the variable wavelength light source 100 is stabilized. This is because light previously passing through the optical filter 210 may be detected through the photo detector 220 (see FIGS. 3 and 4).

According to one aspect of the present embodiment, the wavelength tuning time may output only a value calculated by the photodetector 220 directly. In this case, the photodetector 220 may be transmitted to the wavelength tuning time measuring apparatus 200 from the wavelength variable light source 100, in particular, the wavelength tunable laser driver 120. For example, the wavelength tuning time measuring apparatus 200 includes a separate controller (not shown), and the wavelength change signal is transmitted from the controller to the light detector 220 and the wavelength tunable laser driver (not shown). The time required for the light to pass through the optical filter 210 to the time when the light starts to be stably detected may be determined as the wavelength tuning time.

Alternatively, the photodetector 220 may output only information regarding a time at which light passing through the optical filter 210 starts to be stably sensed. In this case, a separate control unit provided in the wavelength tuning time measuring device 200 may calculate the wavelength tuning time. In this case, it will be apparent to those skilled in the art that information about the time when the wavelength change signal is generated does not need to be transmitted to the photo detector 220.

When the tuning time measuring apparatus 200 having the configuration as shown in FIG. 2 is used, even if the light is emitted from the same tunable light source 100, the wavelength channel range or maximum spectral excursion of the optical filter 210 is provided. Depending on the magnitude, the measured wavelength tuning time may vary. Hereinafter, this will be described in more detail with reference to FIGS. 3 and 4.

3 and 4 respectively show the wave of the light emitted from the tunable light source 100 when the tunable light source 100 (see FIG. 2) tunes from the current wavelength to the target wavelength. 3 is a wave graph of the wavelength of generated light and FIG. 4 is a wave graph of the frequency of generated light. 3 illustrates a case where the wavelength tuning time is changed when the pass wavelength of the optical filter 210 is changed, and FIG. 4 illustrates a case where the wavelength tuning time is changed when the pass frequency of the optical filter 210 is changed. Show it.

Referring to FIG. 3, the first case (I) and the second case (II) are cases in which passbands of the optical filter 210 are different, and the value of the second case (II) is different. Is larger than the first case (I). According to this, the tuning time for case (I), t _a of the first case is greater than the tuning time for case (II), t _b ) of the second case. That is, the wavelength tuning time of the tunable light source 100 may be longer when the passband of the optical filter 210 is set smaller. This means that when the channel wavelength range or maximum spectral excitation is set smaller in the MW PON system, the wavelength variable light source 100 takes longer to tune the wavelength. Therefore, in the link establishment process of the MW PON system, the wavelength tuning time of the tunable light source 100 according to the channel wavelength range or the magnitude of the maximum spectrum excursion of the system should be considered.

4, the third case (III) and the fourth case (IV) are cases where the pass frequency range of the optical filter 210 is different, and thus, the fourth case (III). This is a case where the value of is greater than the third case (III). According to this, the tuning time for case (III), t _c of the third case is greater than the tuning time for case (IV), t _d ) of the fourth case. That is, when the pass frequency range of the optical filter 210 is set small, the wavelength tuning time of the tunable light source 100 may be longer.

5 is a flowchart illustrating an example of a method of measuring a wavelength tuning time of a tunable light source according to an embodiment of the present invention. 5 may be performed using the variable wavelength light source 100 and the wavelength tuning time measuring apparatus 200 illustrated in FIG. 2. The wavelength tuning time may also be determined according to the algorithm described with reference to FIGS. 3 and 4. In the following, the measurement method of the wavelength tuning time will be briefly described in order to prevent unnecessary duplication. Therefore, the matters not described in detail below with respect to the measurement method of the wavelength tuning time may be equally applied to the matters described with reference to FIGS. 2 to 4.

Referring to FIG. 5, first, it is checked whether the center wavelength of the optical filter 210 is set according to the nominal center wavelength of the target channel to be changed (S10). If the central wavelength of the optical filter 210 is properly set, the wavelength of the light generated from the tunable light source is changed (S11). The step S11 may be a process of transmitting a wavelength change signal for changing the second wavelength to the wavelength tunable light source generating the light of the first wavelength. According to the present embodiment, there is no limitation on the subject that transmits such a wavelength change signal to the tunable light source.

As a result of step S11, a time at which light within a predetermined channel wavelength range or maximum spectrum excursion starts to be continuously received is measured (S12). Here, the information indicating the predetermined channel wavelength range or the maximum spectrum excursion may be included in the wavelength change signal transmitted in step S11. As described above, since the light generated by the tunable light source takes some time to stabilize, this step is for measuring the time taken for such stabilization.

Subsequently, the time taken from the time when the wavelength change signal is transmitted in step S11 to step S12 is calculated (S13). This time is a time that must be taken into account in a link establishment procedure for establishing a new link or resetting an existing link to a link of another wavelength in an MW PON system having a tunable light source. According to the present embodiment, as described above, the time required for stabilization may vary depending on the channel wavelength range or the magnitude of the maximum spectrum excursion.

The above description is only an example of the present invention, and the technical idea of the present invention should not be interpreted as being limited by this embodiment. The technical idea of the present invention should be specified only by the invention described in the claims. Therefore, it is apparent to those skilled in the art that the above-described embodiments may be modified and embodied in various forms without departing from the technical spirit of the present invention.

10: OLT 12: WDM
20: ODN 30: ONU
11, 31: variable wavelength light source

Claims (17)

A wavelength tuning time measuring apparatus for measuring a wavelength tuning time of a wavelength tunable light source provided in a multi-wavelength passive optical communication network (MW PON) system,
An optical filter for passing only light of a predetermined wavelength bandwidth; And
A light detector for sensing light passing through the light filter,
The wavelength tuning time is a wavelength tuning time measurement apparatus, characterized in that it takes a time from the time the wavelength change signal is transmitted to the wavelength variable light source to the time when the light is continuously detected by the photo detector. The method of claim 1,
And a transmission bandwidth of the optical filter corresponds to a channel wavelength range, which is a wavelength range required to operate at the performance required for the MW PON system. The method of claim 1,
And a transmission bandwidth of the optical filter corresponds to a channel frequency range, which is a frequency range required to operate at the performance required by the MW PON system. The method of claim 1,
And a transmission bandwidth of the optical filter corresponds to a maximum spectral excursion. The method of claim 1,
And the optical filter is a multilayer thin film filter, a chirped optical waveguide Bragg grating filter, a chirped fiber Bragg grating filter, or an AWG (Arrayed Waveguide Gating) filter. The method of claim 1,
And a center wavelength of the optical filter can be changed. The method of claim 1,
Wherein the wavelength tuning time is utilized in a link establishment procedure or a link change procedure between a service provider device and a subscriber device of the MW PON system. The method of claim 7, wherein
The link change procedure may be performed by powering some OLTs in the MW PON system including a plurality of OLTs when moving to a newly allocated wavelength channel during or after activating the ONU of the MW PON system. When the wavelength channel is shifted to stop the operation in order to operate in the save mode and communicate with other OLTs in operation, and when the MW PON system wants to allocate the wavelength resource dynamically. Or when the output wavelength of the tunable light source drifts or is well maintained within a predetermined grid. A wavelength tuning time measurement method for measuring a wavelength tuning time of a variable wavelength light source provided in a multi-wavelength passive optical communication network (MW PON) system,
Changing a wavelength of light generated from the tunable light source;
Sensing light passing through an optical filter for passing only light of a predetermined wavelength bandwidth; And
And calculating the time taken from the time when the wavelength change signal is transmitted to the variable wavelength light source to the time when light is continuously detected in the sensing step as the wavelength tuning time. 10. The method of claim 9,
The transmission bandwidth of the optical filter corresponds to a channel wavelength range, which is a wavelength range required to operate at the performance required by the MW PON system. 10. The method of claim 9,
And a transmission bandwidth of the optical filter corresponds to a channel frequency range, which is a frequency range required to operate at the performance required by the MW PON system. 10. The method of claim 9,
And a transmission bandwidth of the optical filter corresponds to a maximum spectral excursion. 10. The method of claim 9,
The optical filter is a multilayer thin film filter, a chirped optical waveguide Bragg grating filter, a chirped fiber Bragg grating filter, or an AWG (Arrayed Waveguide Gating) filter. 10. The method of claim 9,
And a center wavelength of the optical filter can be changed. 10. The method of claim 9,
Wherein the wavelength tuning time is utilized in a link establishment procedure or a link change procedure between a service provider device and a subscriber device of the MW PON system. 16. The method of claim 15,
The link change procedure may be performed by powering some OLTs in the MW PON system including a plurality of OLTs when moving to a newly allocated wavelength channel during or after activating the ONU of the MW PON system. When the wavelength channel is shifted to stop the operation in order to operate in the save mode and communicate with other OLTs in operation, and when the MW PON system wants to allocate the wavelength resource dynamically. Or determining the performance such as whether the output wavelength of the tunable light source is drift or well maintained within a predetermined grid. 10. The method of claim 9,
And checking whether the center wavelength of the optical filter is aligned with the center wavelength of the target channel to be changed before changing the wavelength of the tunable light source.

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