KR20150051856A - Method for measuring wavelength tuning time of tunable devices in an optical network and the apparatus thereof - Google Patents

Abstract

The present invention relates to a method for classifying a class of a tunable device through measuring wavelength channel tuning time in a passive optical network (PON) system, and to an apparatus thereof. More specifically, the present invention provides a method and an apparatus thereof, wherein the method enables to measure wavelength channel tuning time of the tunable device when a wavelength channel tuning including a wavelength channel setting, change, initialization, activation, link setting, change, or combination thereof is required with respect to each tunable device for configuring OLT and ONU of a PON, and to classify a class of each tunable device based on the measured tuning time. Accordingly, OLT and ONU are configured with a selective combination of the tunable device of a specific class, thereby having effects of implementing a PON system (1) desired to satisfy an optimal configuration and installation costs, operation and maintenance costs, scalability, power saving, or a combination thereof.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength tunable time measurement method and apparatus for tunable devices used in an optical communication network,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication network in which a wavelength division multiplexing method and a time division multiplexing method are used in combination. More specifically, in the optical communication network using a wavelength variable optical transceiver, a tuning time for a tunable device of a wavelength tunable optical transceiver is measured To a method for classifying wavelength tunable optical transceivers, and to an apparatus therefor.

The proliferation of mobile IP terminals such as smart phones and tablet computers, the commercialization of IPTV services, and the proliferation of multimedia broadcasting / streaming services over the Internet have led to explosive traffic growth. To cope with this problem, it is necessary to efficiently provide services to a larger number of subscribers with limited network resources.

The introduction of broadband optical subscriber networks such as Fiber To The Home (FTTH) and FTTO (Fiber To The Office), which directly connects the central office (CO) and subscribers to optical fiber, has become common. As a method for this, a time division multiplexing (TDM) scheme, a Wavelength Division Multiplexing (WDM) scheme, an Orthogonal Frequency Division Multiplexing (OFDM) scheme, Techniques have been applied to optical network technology.

Particularly, a multi-wavelength passive optical network (MW PON) using a WDM method is attracting much attention.

In a WDM PON or a hybrid PON using a multi-wavelength passive optical communication network, for example, a wavelength multiplexing method, a need exists for a WDM optical transceiver of various wavelengths. The WDM optical transceiver can be implemented in various ways. Among the various implementations, when using a WDM optical transceiver capable of wavelength tuning, it is not necessary to manufacture, install or store an optical transceiver for each wavelength, thereby improving the efficiency of the equipment management and efficiently operating wavelength resources The advantage is added.

However, when using a tunable WDM optical transceiver in an ONU, the output of the WDM optical transceiver or the WDM wavelength that can be received must be set. This wavelength setting may be performed by setting an initial wavelength of the tunable ONU in the process of installing the ONU including the WDM optical transceiver on the subscriber side or by setting the initial wavelength of the wavelength tunable ONU using a protocol between the OLT and the ONU It is possible.

The wavelength setting of the wavelength tunable ONU can be performed through initialization or activation as described above, or when PLOAM message is needed to newly set the wavelength of the tunable ONU in the middle of the service. More specifically, when the OLT-port that was in communication enters the sleep mode for power saving of the system, or when the problem occurs in the corresponding OLT-port, or when the traffic is overloaded to a specific OLT-port, The wavelength tunable ONU that was in communication with the OLT-port needs to be reassigned to another OLT-port, so that it is necessary to change the wavelength being used and reset to a new wavelength. Furthermore, wavelength allocation is performed even when wavelength resources are dynamically allocated for flexible and efficient utilization of wavelength resources.

That is, after the PLOAM message related to the wavelength resetting is transmitted to the wavelength variable ONU, the wavelength used in the wavelength variable ONU is reset and communication with the newly allocated OLT-port is performed. Since the time required for re-setting or changing the wavelength of the wavelength-tunable ONU depends on the detailed description of the wavelength-tunable ONU, the time required for wavelength tuning of the wavelength tunable ONU is classified into a timer setting And so on.

That is, in the OLT, it is possible to check whether a wavelength variable ONU operates properly by checking whether a signal is on the wavelength variable ONU side after a predetermined timer. After the timer set in the wavelength variable ONU, the output wavelength is changed to the reset wavelength channel And transmits the upstream signal to the newly set OLT-port.

In the case of a system in which an optical intensity distributor other than a wavelength-dependent distributor is provided in the ODN, the wavelength resetting is not completed in the wavelength tunable ONU. If the optical transmitter is switched on, an upstream signal is transmitted to another wavelength channel, There is a fear that it may have an adverse effect.

For this reason, it is necessary to measure the time required for wavelength tuning according to the wavelength reset message of the wavelength tunable ONU, and classify the tunable tunable ONU accordingly.

That is, the wavelength tunable ONU can report its variable wavelength class to the OLT so that the OLT can know whether it can perform the specific requirements related to wavelength reset (initialization, protection, load balancing, wavelength dynamic allocation) A system (or network) operator can selectively deliver wavelength-tunable ONUs of a specific class to build a system when building the system.

In order to solve the above problems, it is an object of the present invention to provide a method and apparatus for classifying tunable devices by measuring wavelength tuning time in an optical communication network.

The present invention also provides a method of tuning wavelength tuning time of a tunable device in a case where wavelength tuning including wavelength channel setting, changing, initializing, activating, link setting, changing, or a combination thereof is required for each tunable device of the optical communication network And to provide a method and an apparatus for measurement.

It is another object of the present invention to provide a method and apparatus for classifying each tunable device based on the measured tuning time.

Another object of the present invention is to configure an optical communication network in a selective combination of tunable devices of a specific class through the above method and apparatus.

It is another object of the present invention to provide a method and apparatus for efficiently operating an optical communication network through setting a timer suitable for a class using various tunable devices classified into the class.

According to an aspect of the present invention, there is provided an apparatus for classifying an optical tunable device by measuring a wavelength channel tuning time according to an embodiment of the present invention may be configured according to whether a tunable device is a transmitter or a receiver. At least one wavelength channel tuning time measurement target optical tunable device, when the tunable device is a transmitter; A combination of optical filters capable of converting a wavelength change into a change in light output intensity; At least one photoelectric converter for converting an output of the tunable device into an electrical signal; And a waveform monitor for monitoring the waveform of the electrical signal converted signal. The tunable optical transmitter may further include a control unit for issuing a wavelength channel change command to the optical tunable device.

According to an aspect of the embodiment, the optical tunable device may have a constant temperature function. In one example, the optically tunable device can be placed in a thermostatic chamber. As such, if the optical tunable device has a constant temperature function, the reliability can be improved because the measurement can always be made at a constant temperature.

The controller may be a pulse generator capable of applying a direct current or a voltage so that the output wavelength of the optical tunable device can be changed or a step signal Or may be a device for issuing an output wavelength change command to RS232, I2C, dual port RAM, GPIB or the like.

The wavelength tunable time of the optical tunable device can be defined as a time from a time when a wavelength change command is issued to a time when a target wavelength to be changed, that is, a start time to stably stay in a target wavelength division multiplexing (target WDM) channel. For example, when a wavelength change is photoelectrically converted and a wavelength is measured by an optical intensity, a light intensity measurable in a target WDM channel gradually increases from a point at which a wavelength change command is issued, The time to start may be a wavelength tunable time. (Wavelength channel tuning time: a maximum time taken for the optical power from the tunable device to begin to decrease in the original wavelength channel, where the optical power appears from the tunable device and remains stable within the desired wavelength channel.

The relationship between the wavelength change and the measurable light intensity in the target wavelength division multiple channel is shown in Figs. 8A and 8B. FIG. 8A shows a change in wavelength with time, and FIG. 8B shows a change in optical power with time. However, depending on the combination of optical filters, the view of FIG. 8B may be the same as FIG. 8C.

In FIG. 8C, the initial power and the target power are obtained by normalizing the insertion loss per wavelength division multiplexing of the optical filter set used in the measurement setup, Or not. If not, it may be measured as shown in FIG. 8D. 8C and 8D, X% and Y% may be the same. 8B, 8C, and 8D, the X and Y values are related to the wavelength division multiple channel width and the transmission waveform of the filter used in the optical filter set.

The wavelength tunable time can be expressed as a time index measurable in a waveform monitor as shown in Equation 1 below.

[Equation 1]

(Tl or Tp) + Tr + Tc

In this case, (Tl or Tp) is a time corresponding to a latency time or a processing time taken by the apparatus and method for controlling the output wavelength of the tunable device to change, (Before the wavelength change command is issued) to the point at which the change in the measurable light intensity in the wavelength division multiplexed (WDM) channel begins to occur at X%, and Tc is the wavelength division Tr is the time at which the output wavelength of the tunable device travels (Tl or Tp) to Tc, or the time it takes for the change in measurable light intensity in the multiple (WDM) channel to stabilize within Y% Time.

The photoelectric transducer used in the tunable time measuring device of the tunable device can measure 10 * (1 / Tr) Hz from DC when the wavelength shifts between channels during the variable tuning time of the optical tunable device to be measured, Of the total bandwidth.

The waveform monitor is capable of capturing multi-channel instantaneous signals, so that two channels can be separated and displayed simultaneously on one screen. Wherein the waveform monitor uses a waveform of a signal converted into an electrical signal and a waveform of a signal for applying a wavelength channel change command in a control unit as a trigger signal and displays the waveform channel change time on the waveform monitor, Lt; / RTI > Also, it is possible to arbitrarily select a desired measurement voltage range and a time axis range, and if a signal is not placed in a desired range, the user can be informed whether or not the tunable device satisfies the requirement. In addition, this measurement environment is stored in a nonvolatile memory, and it is possible to use the measurement environment as needed during measurement so that it is not necessary to perform manual operation every time. And the class of the tunable device is distinguished by comparing the electrical signal with respect to the power change of the wavelength channel with time with the wavelength variable mask predetermined according to the class.

In addition, in the tuner device class discriminator through wavelength channel tuning time measurement, the tunable device is a tunable device necessary for configuring an OLT or ONU of a passive optical network system.

In addition, in the class discrimination apparatus of the tunable device through the wavelength channel tuning time measurement, the electrical signal is a value for the power change before the wavelength channel changes and after the wavelength channel changes, The tuning time can be measured by the corresponding value. The power converted value may be normalized and used.

In addition, when the tunable device is a receiver, the apparatus includes at least one photoelectric converter that converts an optical signal into an electric signal, at least one reference transmitter that can be an input and an optical tunable device corresponding to an object to be measured; And a waveform monitor for monitoring a waveform of a signal converted into an electrical signal, wherein the class of the tunable receiver can be identified by comparing the monitoring result with a predetermined wavelength variable mask. The tunable optical receiver may further include a control unit for issuing a wavelength channel change command to the optical tunable device. In addition, the tunable optical receiver can be applied to the tunable optical transmitter in the same manner, and detailed description thereof will be omitted.

Further, in the class discriminator of the tunable device through the measurement of the wavelength channel tuning time, the class is classified into Class 1 (Short: <10 μs), Class 2 (Medium: 10 μs to 25 ms) 25ms to 1s).

In addition, in the class classification device of a tunable device by measuring a wavelength channel tuning time, the class includes a function for reducing the maintenance cost including ONUs that operate independently of wavelength or power saving, PON protection, load balancing, And a tuning time required for performing a function for a combination of the wavelength reallocation function and the wavelength reallocation function.

In addition, in the tunable device class discrimination apparatus through wavelength channel tuning time measurement, the tunable time measurement target tunable device includes one of a tunable transmitter, a tunable receiver, and an optical filter.

In addition, in the class classifier of the tunable device through the measurement of the wavelength channel tuning time, when the tunable time measurement target tunable device is a tunable transmitter, an additional input for test setup at the input or output terminal of the tunable device to be measured Wherein the at least one tunable device comprises at least one or more optical filters, an attenuator, or a combination thereof.

In addition, in the class classifier of the tunable device through the measurement of the wavelength channel tuning time, when the tunable time measurement target tunable device is a tunable transmitter, an additional input for test setup at the input or output terminal of the tunable device to be measured The at least one tunable device can be selectively tested by connecting two AWGs so as to correspond to each other.

In addition, in the class classifying apparatus of the tunable device through the wavelength channel tuning time measurement, when the tunable time measuring target tunable device is a tunable transmitter, the test set-up is performed at the input end or the output end of the tunable- The added at least one tunable device is characterized by being at least one or more optical etalon filters.

In addition, the wavelength channel tuning time measuring apparatus includes at least one wavelength tuning time measurement target tunable device; At least one photoelectric converter for converting an output of the tunable device into an electrical signal; And a waveform monitor for monitoring a signal converted into an electrical signal, wherein the monitoring is performed based on a predetermined tuning mask pattern according to the class of the electrical signal for a power variation of the wavelength channel over time, and the class of the tunable device is distinguished by comparing with the pattern.

The present invention relates to a method of classifying a tunable device in an optical communication network and an apparatus therefor. More particularly, the present invention relates to a method for classifying and classifying tunable devices in an optical communication network by setting, changing, initializing, activating, A tuning device for tuning a wavelength channel of the tunable device and a tuning device for tuning a wavelength of the tunable device based on the measured tuning time, The setting is made suitable for the above-mentioned class, so that it is possible to operate efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an example (a) and another example (b) of a multi-wavelength passive optical network system including a wavelength variable light source.
2 is a flow chart for explaining the concept of wavelength tuning time in a wavelength channel tuning process (procedure);
3 is a waveform diagram for a tuning mask of wavelengths according to an embodiment of the present invention.
4 is an illustration of a class classification for wavelength tuning time according to an embodiment of the present invention;
5 illustrates an exemplary test-setup of an optical transmitter used in the PASCAL tuning time measurement according to an embodiment of the present invention.
6 is a block diagram illustrating a test setup of an optical receiver used in the fuzzy tuning time measurement according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating a measurement result of a power with respect to a wavelength change for measuring a wavelength channel tuning time according to an embodiment of the present invention; FIG.
8A to 8C are graphs showing the relationship between the wavelength change and the measurable light intensity in the target wavelength division multiple channel, respectively.
9A is a block diagram of a measurement setup when a control method of changing the output wavelength of a tunable device with a direct voltage or current using a pulse generator is used.
FIG. 9B is a graph showing information for measuring wavelength tuning time for an arbitrary output wavelength from a starting point of a control signal in the measurement setup of FIG. 9A; FIG. 9C is a block diagram of a measurement setup when a control method of changing the output wavelength of a tunable device using a command via RS232, GPIB, I2C, etc. is used.
FIG. 9D is a graph showing information for measuring wavelength tuning time for an arbitrary output wavelength from a starting point of a control signal in the measurement setup of FIG. 9C; FIG.
FIG. 9E is a block diagram of a measurement setup when a control method of changing the output wavelength of a tunable device using a step signal capable of changing voltage or current is used.
FIG. 9F is a graph showing information for measuring wavelength tuning time for an arbitrary output wavelength from a starting point of a control signal in the measurement setup of FIG. 9E; FIG.

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.

An apparatus or method for measuring wavelength tuning time according to an embodiment of the present invention to be described later can be applied to measuring a variable tuning time or a wavelength tuning time of a wavelength variable light source used in a passive optical communication network system including multiple wavelengths. The wavelength tunable light source is a light source capable of generating light of different wavelengths, such as a wavelength division multiplexing passive optical communication network (WDM PON) system, a hybrid PON combining a TDM scheme and a WDM scheme, for example, a TWDM PON or an OFDM PON system Can be used. The wavelength tuning time in such a PON system is such that when the wavelength variable light source changes the wavelength of light that has already been generated and starts generating light of another wavelength, the light emitted from the wavelength variable light source is stabilized, This means the time required to become.

Changing the wavelength of a tunable light source in an MW PON system may be required in many cases. For example, it may be necessary to change the wavelength of the tunable light source when moving to a newly allocated wavelength channel in the middle or after the activation of the ONU 30 of the MW PON system. As another example, in order to operate some OLTs in a power save mode in an MW PON system including a plurality of OLTs, the operation is suspended and the ONUs 30 connected thereto are moved to a wavelength channel The wavelength of the variable wavelength light source may need to be changed. As another example, when the wavelength resource is dynamically allocated in the MW PON system, or when the output wavelength of the tunable light source drifts or is held well within a predetermined grid, the wavelength tunable light source A wavelength change may be required.

The wavelength tuning process in the MW PON system can be subdivided into the following processes. For example, the wavelength tunable light source of the ONU 30 receives a wavelength variable command from the OLT using a PLOAM or OMCI channel, a wavelength change process, and a subsequent process scheduled after the wavelength change process is completed can do.

The wavelength tuning operation of the wavelength tunable light source may vary depending on the type and configuration of the multi-wavelength passive optical network (MW PON), but may occur in various cases. For example, in the activation process of the ONU 30, the newly activated ONU 30 (more specifically, the wavelength variable light source included in the ONU 30) needs wavelength tuning to the allocated predetermined wavelength . Even after the ONU 30 is activated, the ONU 30 may need to tune wavelengths to newly allocated wavelengths, even if the allocated wavelengths are changed to different wavelengths. The change of the allocated wavelength may be performed by an administrator of the network system for the purpose of managing wavelength resources or may be performed for the purpose of improving performance by load balancing of the network system .

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. 1 (a) and 1 (b), the OLT 10 and each ONU 30) is required. In the process of setting a link, a PLOAM or an OMCI channel can be used. If the process of setting up a link is subdivided, in the process of initializing a wavelength to be used by each ONU 30, And a process of allocating a wavelength to be used by the optical fiber 30. In the link establishment process in the MW PON system 1 including the tunable light source, the wavelength tuning process of the tunable light source (the time required therefor) is also included.

In the MW PON system 1 including the splitter-based ODN 20, the ONU 30, for example, the ONU 30 newly installed in the system can operate only after being assigned an initial wavelength. The initial wavelength may include the wavelength for the downstream and the wavelength for the upstream. This initial wavelength allocation procedure, i.e., wavelength initialization procedure, is essential for activation of each ONU 30. When the new ONU 30 is installed in the ODN 20, the initial downstream wavelength and upstream wavelength are automatically and constantly spaced between the OLT 10 and the new ONU 30 Should be assigned. This wavelength allocation process can be performed as part of the activation of the new ONU 30.

In order for the new ONU 30 to properly communicate with the OLT 10, the downstream wavelength and the upstream wavelength for this new ONU 30 should be specified as soon as possible and wavelength tuning may be required during the activation. In the MW PON system 1 including the ODN 20 based on the AWG (Arrayed Waveguide Gating), only the ODN 20 from the OLT 10 to the ONU 30 or from the ONU 30 to the OLT 10 Only one wavelength can pass. In this case, the wavelength assignment may be done during the physical installation process.

If a certain wavelength in the MW PON system 1 is in an idle state in the case of low or heavy traffic, and a heavy load is applied to other wavelengths, all or a part of the ONUs 30 to which the load- Providing a load balance that varies the ONU 30 to an idle wavelength may be an example of changing the wavelength assigned to the ONU 30. [ According to this, traffic can be balanced between available wavelengths and the PON operation can be maintained in a stable state. Alternatively, if most of the wavelengths are used in the MW PON system 1, but the traffic is small at each wavelength, the MW PON system 1 can be efficiently operated by reducing the wavelength used. In this case, an effect of saving the power of the OLT 10 can be obtained by turning off any port of the OLT 10 and varying the ONU 30 into a subset of available wavelengths.

The process of setting or resetting the link in the MW PON system 1 includes a process from when the OLT 10 or the ONU 30 having a tunable light source generates light to stably generate light at a predetermined wavelength allocated thereto In wavelength tuning process. The wavelength tuning or wavelength tuning of the wavelength tunable light source involves oscillating the light of the wavelength assigned to the ONU 30 in the link setting process in the MW PON system 1 as well as changing the wavelength of the light oscillated to the newly allocated wavelength do. For this purpose, a tunable light source or wavelength variable optical transceiver may be installed in the ONU 30 and / or the OLT 10 of the MW PON system 1. [

However, in the wavelength tuning process, the wavelength tuning time may be different in the kind, characteristic, grade, etc. of the wavelength variable light source. Therefore, the wavelength tuning time of the wavelength variable light source provided in the MW PON system 1 must be considered in the link establishment process between the OLT 10 and the ONU 30. That is, the wavelength tunable laser to be used in the MW PON system 1 in which the tuning is frequently performed due to the dynamic allocation of the wavelength or the like can be a performance parameter in which the wavelength tuning time is very important. For example, the MW PON system 1 may be divided into a plurality of classes according to a wavelength tuning speed or a wavelength tuning time. Since the wavelength tuning time may vary depending on the method of measurement, a uniform method of measuring the wavelength tuning time for the variable wavelength light source and a device implementing the same are required. And the wavelength tuning time of the tunable light source must meet the time required by the MW PON system (1).

For this wavelength tuning process, it is necessary to clearly define the tuning time. Hereinafter, a method for clearly defining the wavelength channel tuning time will be described.

2 is a flow chart for explaining the concept of wavelength tuning time in the wavelength channel tuning process (procedure). First, when a wavelength channel change command is transmitted from the OLT 10 to the ONU 30, the ONU 30 performs a wavelength channel tuning procedure and sends a response to the OLT 10 with respect to the wavelength channel tuning procedure. That is, the wavelength channel tuning procedure for the tunable transmitter of the ONU 30 will be described in detail. The wavelength channel tuning is performed according to the following steps.

Step 1: Receive a command from the OLT 10.

Step 2: Turn off the tunable transmitter.

Step 3: Tuning or slewing to a new wavelength channel. In this case, the starting part is the part beyond the pass band of the current wavelength channel, the main part is the part which is slewing to the new wavelength channel, and the last part is the part which is going to stop in the new wavelength channel.

Step 4: Stay within the new wavelength channel.

Step 5: Re-establish the downstream framing from the OLT 10.

Step 6: Turn on the tunable transmitter and start communication with the OLT 10.

Step 7: Perform fine tuning (or recalibration).

Here, the time taken in step 3 is the same as the time taken by the tunable device using the same mechanism (thermal, mechanical, current injection, etc.). This time is referred to as a transition time or a tuning time, which is derived from the tuning distance and the tuning speed. The time taken in step 4 is different for each device because it uses different control techniques for each device. Though implementation issues are relevant to vendors, standards should be clear enough to guide which tunable devices belong to which tuning classes. Therefore, it is necessary to name the "tuning time" more precisely as "wavelength channel tuning time ".

In the present invention, a method of measuring the time from step 1 to step 4 and a measurement setup are described. In this case, since the time taken in step 2 is negligible compared to the time spent in steps 3 and 4, which is several tens to several tens of ns, in the case of the apparatus for measuring the tuning time of the tunable device, Make sure that the transmitter of the tunable device is turned on without turning off the power.

Therefore, in the present invention, the wavelength tuning time is defined as "the optical power of the tunable laser is tuned to the desired wavelength channel after deviating from the original wavelength channel after receiving the wavelength channel changing signal and stably remains in the required wavelength channel (The maximum allowed time taken for the time to reach the wavelength of the optical fiber), the optical wavelength of the tunable laser, stably remains within the desired wavelength channel. "

In order to actually measure the wavelength channel time according to the definition of the wavelength channel tuning time, the following relation can be derived.

That is, the wavelength channel tuning time = uncertain time + (N * CS - 2 * MSE) + final interval time, where the uncertain time includes the starting portion and some electrical delay time, ) Will most likely be a physically fixed value according to the tuning mechanism, and the final interval time will depend on the control circuitry for the tunable device.

A common feature among most NG-PON2 receptions is the ability to tune the transmitter, the receiver, or both. In the downstream direction from the OLT to the ONU, the tunable ONU receiver needs to select an appropriate channel. In the upward direction from the ONU to the OLT, the ONU transmitter is tuned to output the required channel. The OLT receiver channel selection capability may vary depending on the NG-PON2 approach. Center frequency, center frequency dispersion, channel spacing, and tuning characteristics, and the tuning times of the transmitter and the receiver are classified into three classes. These classes have different application cases in each case.

As shown in FIG. 3, the general tuning mask of the NG-PON2 ONU can be used to classify various tunable transmitters or receivers into different tuning classes, which are classified into three sections in FIG. The test setup of the optical transmitter for measuring the tuning time using the wavelength tuning mask is shown in Fig.

The purpose of using the tuning mask is to easily discriminate the wavelength variable class of the tunable device as in the case of using the eye mask to determine the performance index of the existing optical transmitter.

3, the maximum value held before the wavelength tuning is set to a level 301 before the tuning, and the maximum value maintained after the tuning is set to the first level 302 after the tuning, , The time difference of the level 304 corresponding to Y% of one level after the wavelength tuning from the time when the tunable command is applied to the tunable device can be referred to as a wavelength channel tuning time.

One level after wavelength tuning can be found by analyzing with a horizontal histogram. The value corresponding to Y is a value between 0 and 1, which may vary depending on the transmission bandwidth and transmission spectrum of the optical filter set used in the measurement setup, taking into account the WDM wavelength channel width of the system in which the tunable device is to be used.

That is, when the user inputs the information of the system in which the tunable device to be measured is to be used, the Y value is automatically calculated, and the tuning time can be automatically calculated from the measured value. Also, this process is compared with the tuning pattern of the tuning time according to the class of the predefined class, using the wavelength tuning mask, and the result shows that the corresponding tunable device corresponds to which class, Can be measured. In the present invention, the measurement of the tuning time by the wavelength tuning mask is merely an example. Therefore, when the tuning time is measured, the end point of the rising edge is set to be the end point, spectral excursion, and so on.

The wavelength tuning time value set in the class of FIG. 4 is divided into three classes, and the tuning time corresponding to each class is presented. However, this is only one example, and the class is defined more finely It is also possible to do. That is, when a user sets a criterion for a specific class through a device according to the present invention and measures the tuning time, the class is output according to the measured tuning time, You can check if it is applicable. The verification of these classes may be specified in the product of the tunable device, specifically through the verification and validation of the certification authority. In this way, when each ONU is configured using the corresponding tunable device, it is also possible to notify the OLT of the corresponding class information and collect the class information of the ONU. Thus, according to the OLT, Timers can be set for channel change, initialization, and activation, which plays a very important role in the efficient use of network systems.

Hereinafter, how the tuning time described above can be specifically defined will be described. The wavelength channel tuning time according to an embodiment of the present invention corresponds to a range from N * CS + 2 * MSE to N * CS-2 * MSE. Where N is the channel count, CS is the channel spacing in GHz, and MSE is the maximum spectral excitation in GHz. This range is simply difficult to express as a simple expression such as N * CS-2 * MSE or N * CS + 2 * MSE. The wavelength tuning time means the maximum allowed time allowed for the tuning tunable device to tune in the relevant step. The tuning time described above is the time required for each device to tune from any wavelength to any other wavelength within the maximum tuned spectral excursions for each wavelength at a particular ambient temperature. The tuning time will have different characteristics depending on the use during ranging, wavelength change and fine tuning of the wavelength. The ONU tuning time can be measured using the procedure and test setup described below. The purpose of the test setup is to measure the tuning time without ambiguity. Of course, measurements are made for long wavelengths to short wavelengths.

5 is a block diagram illustrating a test setup for tuning time of an ONU transmitter for measuring a wavelength channel tuning time according to an embodiment of the present invention.

Hereinafter, a method for measuring a tuning time of a wavelength channel according to the present invention will be described. FIG. 5 shows an example of various tunable devices that need to measure the wavelength channel tuning time. In the case of FIG. 5, the tunable transmitter 511, 521, 531, and 541 are DUTs. In other words, it is necessary to configure various network environments to measure DUT tuning time and to measure corresponding DUT. 5, the attenuator 502 may be disposed between the optical filters 504 and 507 and the O / E converters 505 and 508.

FIG. 5A illustrates a case in which two optical filters 505 and 508 are used as a DUT with the tunable optical transmitter 501. FIG. In this case, the power for the two wavelengths is combined 510. In this case, the tuning time can be easily classified by classifying the tuning time using the wavelength tuning diagram of the present invention.

5 (b) is a test setup with a tunable optical transmitter including a single optical transmitter 511 and optical filter 513 as a DUT. In this case, the tuning time can be easily measured by using the wavelength tuning diagram according to the present invention.

Next, in the measurement of the wavelength channel tuning time of the tunable optical transmitter (tunable Tx), various configurations of the optical filters are shown in Figs. 5 (c) to 5 (e). 5C shows a case where the filters 1 and 2 526 and 527 and the combiner 528 are inserted and a variable attenuator 523 is provided to generate various path loss. Can be measured by the oscilloscopes 525 and 530. Here, the filter 1 526, the filter 2 527, and the attenuator 523 are connected to each other. However, the number of the optical filters, the number of the attenuators, and the degree of attenuation can be variously set. In addition, the center wavelengths of the optical filter 1 and the optical filter 2 can be tunable, which can be set according to the conditions to be measured. Also, the responsibilities of the photoelectric converters 524 and 529 should be the same. The advantage of this test setup is that it is normal to normalize using some of the tunable lasers that do not pass through the wavelength filter. For example, it is possible to calibrate a tunable laser even if the wavelength of the tunable laser changes. However, if the amount of change of the output light intensity according to the wavelength of the tunable laser can be known in advance, it is not necessary to measure it.

5 (d) shows a structure in which the AWG is connected in a second stage (532, 533). In this case, since the AWG can establish a 1: N connection, have. That is, it is possible to measure the tuning time of the tunable optical transmitter 531 after forming connection relationships of various AWGs.

5E illustrates a test-setup using an Etalon filter 542, which measures the tunable wavelength tuning time of the tunable optical transmitter according to the transmission characteristics of various etalon filters, The class for the tuning time of the transmitter 541 can be distinguished.

FIG. 6 shows a test setup in the case of an optical receiver, where the DUT is an optical filter, in which case the test-setup of the ONU can be configured while varying the configuration of the tunable transmitter.

In order to measure the wavelength channel tuning time of the tunable filter, a laser set for referencing 601 and an oscilloscope 605 for measuring time are required as shown in FIG. Here, the attenuator 602 may be used. If the attenuator 602 is required, the output of the optical filter 603 to be measured is photoelectrically converted (604) by receiving an output of various kinds of optical transmitters 601, By measuring the change (605), the tuning time according to the wavelength channel conversion of the optical filter 603 can be measured. This embodiment is different from the other embodiments in that the tunable filter is a DUT, and the optical transmitter may be constituted by various laser sets or may be constituted by an optical transmitter having a light output of a central wavelength of a target WDM channel.

5 and 6 may include a tunable optical transmitter, an optical transmitter, a tunable optical filter, an optical filter, an optical multiplexer, an optical demultiplexer, or a combination thereof, and FIGS. 5 and 6 It is only an example of various optical devices for measuring the tuning time. If the method of measuring the tuning time of the present invention is used, the classifying of the measured tuning time into classes for various optical devices is, of course, It is to be understood that the invention is not limited thereto.

FIG. 7 is a diagram illustrating a result of measurement of power with respect to a wavelength change for measuring a wavelength channel tuning time according to an embodiment of the present invention. In an experiment using a TEC-controlled DFB-laser, Shows an example of a waveform obtained by measuring the tuning time according to the present invention.

7 is a wavelength tuning mask in the case where one level before wavelength tuning and one level after wavelength tuning do not coincide with each other. For optical tunable devices, the optical power intensity or insertion loss due to wavelength tuning may be different. In this case, unlike FIG. 3, one level before and after wavelength tuning can be expressed differently. In this case, although the wavelength tunable time can be measured after normalizing and matching one level before and after the tuning of the wavelength, it is also possible to hold the wavelength command as the start point without applying the normalization to the tunable device, It is also possible to mark the difference between the two as the tuning time by taking the point at which the measured value on the monitor corresponds to the Y value of the final target value as the end point.

The Y value is a value that can be changed according to the transmission bandwidth and the shape of the transmission spectrum of the optical filter set used in the tuning apparatus. That is, if the spectral excitation of the WDM channel of the system in which the tunable device is to be used is determined, the insertion loss value of the optical filter at the spectral excursion point may be measured in advance and utilized as the Y value used for determining the tuning time .

When the optical filter set used in the wavelength tuning time measuring device transmits the initial wavelength of the tunable device and is also configured to transmit the final wavelength, a change in the optical intensity, which occurs due to the wavelength variation with time, Respectively.

Unlike FIG. 3, which normalizes the power change over the wavelength, the case of FIG. 7 is not normalized. This result can be obtained as shown in FIG. 7 when there is a difference in insertion loss according to the wavelength of the optical filter set used in the measuring apparatus or when the tunable device changes the output intensity according to the wavelength. More specifically, these measurements can be obtained by increasing or decreasing the temperature of the DFB laser without using the auto power control (APC) function in the DFB laser to vary the wavelength channel.

The present invention relates to a method for measuring a tuning time according to a wavelength channel change for a tunable device in an optical communication network and dividing the tuning time into a predetermined class and then identifying a class to which the tunable device belongs and a device using the method It is suggested.

Each of the tunable devices divided into the above classes is required to set a timer value required in link establishment, initialization and link activation in the optical communication network, and efficient network operation is possible by setting a timer according to the tuning time of the tuning device.

The tuning time measurement procedure according to an embodiment of the present invention is as follows.

First, the control method of the tunable device is determined.

If you want to use a control method that changes the output wavelength of the tunable device with a direct voltage or current using a pulse generator, prepare the measurement setup as shown in Figure 9a. FIG. 9B is a graph showing information for measuring the wavelength tuning time for an arbitrary output wavelength from the starting point of the control signal in the measurement setup of FIG. 9A. FIG.

Referring to FIGS. 9A and 9B, the devices of the measurement setup, including the tunable device, are preheated by pre-turning on to stabilize.

If the output light intensity of the tunable device is too high, place a variable optical attenuator at the front of the optical filter set or at the front of the O / E converter so that the O / E converter is not overloaded.

Specify the initial wavelength and target wavelength to measure the tuning time. Check the transmission wavelengths of the optical filter set of the measurement setup and confirm once more whether the target wavelength is the transmissible wavelength.

Determine how much voltage or current should be applied to the tunable device to move from the intial wavelength to the target wavelength, and then set the pulse generator to apply the corresponding voltage or current.

The pulse generator is driven so that the set voltage or current can be applied to the tunable device.

Check the waveform change on the waveform monitor and calculate the tuning time (Tt). The Y value may vary depending on the WDM channel width of the system in which the tunable device is to be used, the transmission width and the transmission spectrum of the optical filter used in the measurement apparatus, and the user may select the specification of the system in which the tunable device is to be used And may be set to be automatically calculated.

If necessary, perform the above procedure two or more times to take an average value.

Check tuning class of tunable device with average tuning time.

The tuning time of the tunable device measured according to necessity may be preliminarily programmed so that the tuning time margin for keeping the tuning class is indicated.

If you want to use a control method that changes the output wavelength of the tunable device using command via RS232, GPIB, I2C, etc., prepare the measurement setup as shown in Fig. 9c. FIG. 9D is a graph showing information for measuring wavelength tuning time for an arbitrary output wavelength from a starting point of a control signal in the measurement setup of FIG. 9C. FIG.

Referring to Figures 9c and 9d, the devices of the measurement setup, including the tunable device, are preheated by pre-warming to stabilize.

If the output light intensity of the tunable device is too high, place a variable optical attenuator at the front of the optical filter set or at the front of the O / E converter so that the O / E converter is not overloaded.

Specify the initial wavelength and target wavelength to measure the tuning time. Check the transmission wavelengths of the optical filter set of the measurement setup and confirm once more whether the target wavelength is the transmissible wavelength.

To determine the command to be sent to the tunable device to move from the intial wavelength to the target wavelength, the command is sent down.

Check the waveform change on the waveform monitor and calculate the tuning time (Tt). At this time, a command sending flag or a command completer flag can be used to calculate the processing time (Tp) corresponding to a part of the tuning time. The Y value may vary depending on the WDM channel width of the system in which the tunable device is to be used, the transmission width and the transmission spectrum of the optical filter used in the measurement apparatus, and the user may select the specification of the system in which the tunable device is to be used And may be set to be automatically calculated.

If necessary, perform the above procedure two or more times to take an average value.

Check tuning class of tunable device with average tuning time.

The tuning time of the tunable device measured according to necessity may be preliminarily programmed so that the tuning time margin for keeping the tuning class is indicated.

If you want to use a control method that changes the output wavelength of the tunable device using a step signal that can change the voltage or current, prepare the measurement setup as shown in Figure 9e. FIG. 9F is a graph showing information for measuring the wavelength tuning time for an arbitrary output wavelength from the starting point of the control signal in the measurement setup of FIG. 9E. FIG.

Referring to Figures 9E and 9F, the devices of the measurement setup, including the tunable device, are preheated by pre-warming to stabilize.

If the output light intensity of the tunable device is too high, place a variable optical attenuator at the front of the optical filter set or at the front of the O / E converter so that the O / E converter is not overloaded.

Specify the initial wavelength and target wavelength to measure the tuning time. Check the transmission wavelengths of the optical filter set of the measurement setup and confirm once more whether the target wavelength is the transmissible wavelength.

Determine the size of the signal to be sent to the tunable device to move from the intial wavelength to the target wavelength and apply it.

Check the waveform change on the waveform monitor and calculate the tuning time (Tt). The Y value may vary depending on the WDM channel width of the system in which the tunable device is to be used, the transmission width and the transmission spectrum of the optical filter used in the measurement apparatus, and the user may select the specification of the system in which the tunable device is to be used And may be set to be automatically calculated.

If necessary, perform the above procedure two or more times to take an average value.

Check tuning class of tunable device with average tuning time.

The tuning time of the tunable device measured according to necessity may be preliminarily programmed so that the tuning time margin for keeping the tuning class is indicated.

The above description is only an example of the present invention, and the technical idea of the present invention should not be construed as being limited by these embodiments. The technical idea of the present invention should be specified only by the invention described in the claims. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention.

1: Passive optical network system
10: OLT 20: ODN 30: ONU
501, 511, 521, 531, 541: Optical transmitter
502, 512, 522: attenuator
504, 507, 513, 526, 527, 542: optical filter
505, 508, 514, 524, 529, 534, 543:
506, 509, 515, 525, 530, 535, 544: Waveform monitor (oscilloscope, scope)

Claims (1)

At least one wavelength channel tuning time measurement object optical tunable device;
A combination of optical filters capable of converting a wavelength change into a change in light output intensity;
At least one photoelectric converter for converting an output of the tunable device into an electrical signal;
A waveform monitor for monitoring a waveform of a signal converted to an electrical signal; And
And a control unit for issuing a wavelength channel change command to the optical tunable device.

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