KR20150051870A

KR20150051870A - Method for measuring wavelength tuning time of tunable devices in an optical network and the system thereof

Info

Publication number: KR20150051870A
Application number: KR1020140137895A
Authority: KR
Inventors: 이지현; 이한협; 이은구; 두경환
Original assignee: 한국전자통신연구원
Priority date: 2013-11-04
Filing date: 2014-10-13
Publication date: 2015-05-13

Abstract

Disclosed are a method for measuring a wavelength channel tuning time by using an optical filter that converts a change in an output wavelength of a tunable device into an optical intensity change, and a system thereof. The system for measuring a wavelength channel tuning time comprises: an optical filter set configured to convert a wavelength change in an optical tunable device into an optical output intensity change; an optical electric converter configured to convert the optical output intensity change output by the optical filter set into an electric signal; and a controller configured to generate a wavelength change command applied to the tunable device, so as to calculate a wavelength channel tuning time of the tunable device by using the wavelength change command and the electric signal output by the optical electric converter.

Description

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

The present invention relates to a method for measuring wavelength tuning time of a tunable device used in an optical communication network and a system therefor, and more particularly, to an optical filter for converting a change in output wavelength of a tunable device into a change in optical intensity And a system for measuring the tuning time of a wavelength channel.

As a result of the development of optical communication technology and the rapid increase of Internet service demand, basic researches on the optical access network have been conducted since the early 2000s. As a result, FTTH (Fiber To The Home (FTTO), and Fiber To The Office (FTTO).

At the same time, 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, In order to cope with traffic increase, researches on next generation high-speed, high-capacity optical access network technology are being actively carried out.

Time Division Multiplexing (TDM) scheme and wavelength division multiplexing (WDM) schemes are applied to optical network technology to efficiently provide services to more subscribers with limited network resources have. Recently, optical subscriber networks (TDM) and WDM techniques have been studied.

Hybrid time and wavelength division multiplexing (TWDM) optical network technology, which is applied together with dual TDM and WDM techniques, can meet the demand for bandwidth expansion of a continuous network and provides high-speed communication services to a large number of subscribers, The number of subscribers can be easily expanded. Therefore, much research has been conducted on time and wavelength division multiplexing (TWDM) optical access network technologies as candidates for the next generation optical network technology after the 10G passive optical network technology.

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 various implementations, when a wavelength tunable WDM optical transceiver is used, it is not necessary to manufacture an optical transceiver for each wavelength, so that the efficiency of the equipment management is improved and the wavelength resource can be efficiently operated.

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 can be performed by setting the initial wavelength of the initial wavelength tunable ONU of the tunable ONU in the process of installing the ONU including the WDM optical transceiver on the subscriber side or by setting the wavelength of the wavelength tunable ONU using the protocol between the OLT and the ONU The initial wavelength can also be set.

The wavelength setting of the wavelength tunable ONU can be performed through the initialization or activation as described above, or when the wavelength used in the wavelength tunable ONU needs to be newly set in the middle of the service through the PLOAM message. 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 ODN is equipped with a light intensity distributor other than a wavelength-dependent splitter, if wavelength tuning is not completed in the tunable ONU, if the optical transmitter is switched on, upstream signals are transmitted to other wavelength channels, .

For this reason, it is necessary to measure the time required for the variable according to the wavelength reset message of the wavelength tunable ONU, and to classify the wavelength tunable ONU into a class.

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) When a system (or network) operator rescues the system, the wavelength tunable ONU of a certain class can be selectively delivered to the system.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wavelength channel tuning time measurement method and system for a tunable device used in an optical communication network.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

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 apparatus may further include a controller 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 tuning time of the optical tunable device can be defined as a time from a time point at which a wavelength change command is issued to a time point at which 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 wavelength tuning time may be the time taken to initiate the wavelength tuning. The wavelength tuning time may be the maximum time taken for the optical tunable device to begin to decrease in the original wavelength channel, The time when the optical power appears from the tunable device is stable within the desired wavelength channel.

9D, the initial power and 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. 9B. 9B, 9D, and f, X% and Y% may be the same. And 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 channel tuning time is expressed by a measurable time index in the waveform monitor, which is _{equal to} T _p (or T _l ) + T _tr + T _c .

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 T _tr is the time at which the output wavelength of the tunable device moves, from the time after Tp to the time when Tc (t) is the time required for the change in the measurable light intensity in the division multiple (WDM) channel to stabilize within Y% It is the time before.

In the photoelectric transducer used in the tunable time measuring device of a tunable device, when the wavelength tuning time of the optical tunable device to be measured is T _tr , _tr ) Hz.

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, the user can select a desired measurement voltage range and a time axis range, and if the user does not place a signal 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 mask for wavelength variable time measurement determined in advance according to the class.

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

Also, 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, and the monitored signal is the power change So that the tuning time can be measured. 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) and Class 3 : 25 ms to 1 s).

In addition, in the tuner device class classification device through wavelength channel tuning time measurement, the class includes a function for reducing maintenance costs including ONUs or power saving that are independent of wavelength, PON protection, load balancing, variable bandwidth A wavelength reallocation function including allocation, or a tuning time required for performing a function for a combination thereof.

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, or a tunable optical filter.

In addition, in the class classifier of the tunable device through the wavelength channel tuning time measurement, if the tunable time measurement target tunable device is a tunable transmitter, it is added for test setup at the output terminal of the tunable time measurement target tunable device The at least one optical filter may include at least one or more of the at least one attenuator or a combination thereof.

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, at least The at least one optical filter can be selectively tested by connecting the two AWGs so as to correspond to each other.

In addition, in the class classifier of the tunable device through the wavelength channel tuning time measurement, if the tunable time measurement target tunable device is a tunable transmitter, it is added for test setup at the output terminal of the tunable time measurement target tunable device The at least one optical filter is characterized by being at least one or more optical etalon filters.

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 receiver, it is added to the input terminal of the tunable time measuring target device for test setup At least one reference optical transmitter, at least one attenuator, or a combination thereof.

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 optical filter, the input of the tuning time measuring target tunable device is added At least one reference optical transmitter, at least one attenuator, or a combination thereof.

In addition, the wavelength channel tuning time measuring apparatus includes at least one wavelength tuning time measurement target tunable device; At least one reference 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 of 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 a wavelength channel tuning time in a wavelength channel tuning process (procedure);
3 is a diagram illustrating an example in which a tuning mask is applied to a change in light intensity according to a change in a measured wavelength according to an embodiment of the present invention.
FIG. 4 illustrates an example of a test-setup used to measure a wavelength channel tuning time of a wavelength tunable optical transmitter according to an exemplary embodiment of the present invention; FIG.
5 is a block diagram illustrating a test setup used for wavelength channel tuning time measurement of a wavelength tunable optical filter in accordance with an embodiment of the present invention.
6 is a block diagram illustrating a wavelength channel tuning time measurement system of a tunable device in accordance with another embodiment of the present invention.
FIG. 7 is a diagram illustrating a result of measuring a change in light intensity according to a change in wavelength in an embodiment of the present invention; FIG.
FIG. 8 is an exemplary view showing another result of measuring a change in light intensity according to a change in wavelength in an embodiment of the present invention; FIG.
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 the wavelength channel tuning time for an arbitrary output wavelength from the starting point of the 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 the wavelength channel tuning time for an arbitrary output wavelength from the starting point of the 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 a wavelength channel tuning time for an arbitrary output wavelength from a starting point of a control signal in the measurement setup of FIG. 9E. FIG.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. And is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined by the claims. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. It is noted that " comprises, " or "comprising," as used herein, means the presence or absence of one or more other components, steps, operations, and / Do not exclude the addition.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals refer to like elements throughout. In the drawings, like reference numerals are used to denote like elements, and in the description of the present invention, In the following description, a detailed description of the present invention will be omitted.

An apparatus or method for measuring a wavelength channel tuning time according to an embodiment of the present invention to be described later can be applied to measure a wavelength channel tuning time or a wavelength channel tuning time of a wavelength tunable device used in a passive optical network system including multiple wavelengths. The wavelength tunable device may be one of a tunable light source or a tunable optical transmitter, a tunable optical receiver, or a tunable filter.

A variable wavelength light source or a variable wavelength optical transmitter is a light source or an optical transmitter capable of selectively generating light of different wavelengths, the wavelength variable optical receiver is an optical receiver capable of selectively receiving light of different wavelengths, A filter is an optical filter capable of selectively transmitting light of different wavelengths.

Such a wavelength tunable device can be used not only in a wavelength division multiplexing passive optical network (WDM PON) system but also in a hybrid PON in which a TDM scheme and a WDM scheme are combined, for example, a TWDM PON or an OFDM PON system. A PON system using such a WDM scheme will be referred to as a multi-wavelength PON system in this specification.

The wavelength tuning time in the PON system means the time required for the wavelength tunable device to move from the time when the command is received to change the operating wavelength that is being used to the newly allocated wavelength channel to the stable wavelength.

Changing the operating wavelength of a tunable device in an MW PON system may be required in many cases. For example, when the ONU 30 of the MW PON system is composed of at least one or more wavelength tunable devices, when moving to a newly allocated wavelength channel in the middle or after the activation process, Operating wavelength changes may be required.

As another example, in order to operate some OLTs in a power save mode in a MW PON system including a plurality of OLTs, the wavelength tunable ONUs 30 are stopped to operate, It may be necessary to change the operating wavelength of the wavelength variable device.

As another example, in the case where the wavelength resource is dynamically allocated in the MW PON system, or when the operation wavelength of the wavelength tunable device is drifted or is well maintained within a predetermined grid, A wavelength change may be required.

The wavelength tuning process in the MW PON system can be subdivided into the following processes. For example, a process in which the ONU 30 having a wavelength tunable function receives a wavelength variable command from the OLT using a PLOAM or OMCI channel, a process in which a wavelength is changed, a process in which a subsequent scheduled process is performed after the wavelength change is completed . &Lt; / RTI >

The wavelength tuning operation of the wavelength tunable device may vary depending on the type and configuration of the multi-wavelength passive optical network (MW PON).

For example, an ONU 30 (more specifically, a wavelength tunable device included in the ONU 30) activated in the activation process of the ONU 30 is required to perform 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, each ONU 30 initializes a wavelength to be used by the OLT 10, And a process of assigning a wavelength to be used.

In the link establishment process in the MW PON system 1 including the tunable device, the wavelength tuning process of the tunable device (time required thereby) is also included.

In the MW PON system 1 including the splitter-based ODN 20, 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.

On the other hand, for the communication from the OLT 10 to the ONU 30 or from the ONU 30 to the OLT 10 in the MW PON system 1 including the ODN 20 based on the AWG (Arrayed Waveguide Gating) In the ODN 20, 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, it is possible to obtain the effect of saving the power of the OLT 10 by turning off any port of the OLT 10 and varying the ONU 30 into a subset of available wavelengths.

The link setting or resetting process in the MW PON system 1 is performed by the OLT 10 or the ONU 30 having the tunable device until the wavelength tuning is performed, &Lt; / RTI > The wavelength tuning or wavelength tuning of the wavelength tunable device means that the operating wavelength is changed from the wavelength channel allocated to the ONU 30 in the link setting process, that is, the wavelength channel newly allocated in the wavelength channel that was being operated in the MW PON system 1 . To this end, the ONU 30 and / or the OLT 10 of the MW PON system 1 may be equipped with one or more tunable devices.

However, in the wavelength tuning process, the wavelength channel tuning time may be different depending on the type, characteristics, control method, etc. of the wavelength variable device. Therefore, the wavelength channel tuning time of the tunable device included in the MW PON system 1 must be considered in the link establishment process between the OLT 10 and the ONU 30.

That is, wavelength tuning time can be a very important performance parameter in a wavelength variable device to be used in the MW PON system 1 in which wavelength tuning is frequently performed due to wavelength dynamic allocation or the like, and a plurality of It may be classified into grades. Since the tuning time of the wavelength channel may vary depending on the method of measurement, a uniform method of measuring the wavelength channel tuning time for the tunable device and a device implementing the tuning method are required. And the wavelength channel tuning time of the tunable device must meet the wavelength tunable time requirements required by the MW PON system (1) in which the tunable device is to be used.

For this wavelength channel 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 a concept of a wavelength channel tuning time in a 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 returns the result to the OLT 10.

In the present specification, an ONU described later refers to a wavelength variable ONU constituted by one or more wavelength tunable devices, and a wavelength tunable ONU including a tunable transmitter and a tunable optical receiver will be described as an example.

The wavelength channel tuning procedure of the ONU 30 will be described in detail. The wavelength channel tuning is performed according to the following steps.

Step 1: Receive a wavelength channel change command from the OLT 10.

Step 2: Turn off the tunable transmitter.

Step 3: In order to change the operating wavelength to the new wavelength channel, it starts to deviate from the previously used operating wavelength and arrives at the newly allocated wavelength channel.

Step 4: Get to the newly assigned wavelength channel and use it as the new operating wavelength.

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).

It should be noted that the operation wavelength transfer procedure in steps 3 and 4 corresponds to both the wavelength tunable transmitter and the tunable receiver, and the wavelength tunable time of the tunable transmitter and the wavelength tunable receiver may be different.

Also, for a tunable device using the same mechanism (thermal, mechanical, current injection, etc.), the time taken in step 3 has the same value. This time is referred to as the transition time, which is derived from the tuning distance and the tuning speed.

The time taken in step 4 is the time taken for the wavelength tunable device to stabilize after transferring the operating wavelength stably to the newly allocated wavelength channel, which can be called a convergence time. This depends on the tunable device wavelength tunable mechanism as well as on the control technique, and can have different values.

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 and a measurement system (a set-up) for measuring the time from one step to step four of a wavelength tunable device are presented. In this case, since the time taken in step 2 is negligible in comparison with the time taken in steps 3 and 4, which is several tens to several tens of nanoseconds, it is excluded in the variable tuning time.

That is, in the present invention, the wavelength tuning time is defined as "after the tunable device receives a signal to change the operating wavelength channel, it moves out of the originally operating wavelength channel and moves to the newly allocated wavelength channel, The maximum allowable time to be fulfilled ".

When the tunable device is a tunable optical transmitter, it receives a command signal to change the operating wavelength channel, and then allows the maximum allowed until the optical power output is stably maintained in the newly allocated wavelength channel after leaving the originally operating wavelength channel It means time. And a tunable wavelength tunable to the desired wavelength channel and 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

Where the uncertain time includes the start portion and some electrical delay time, the time for (N * CS - 2 * MSE) will be mostly physically fixed according to the tuning mechanism, Will depend on the control circuitry for the tunable device.

A common feature among most NG-PON2 approaches 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. The tuning time of the transmitter and the receiver are classified into a plurality of classes, and these classes have different application cases in each case.

A variation in light intensity with a change in the measured wavelength according to an embodiment of the present invention is illustrated by way of example in FIG.

Referring to FIG. 3, the wavelength tuning time can be measured by applying a tuning mask to a change in the measured light intensity, and a maximum value held before the wavelength tuning in the tuning mask is set to a level 301 before tuning , And a maximum value retained after the tuning of the wavelength is defined as a first level 302 after the tuning of the wavelength, a level corresponding to Y% of one level after wavelength tuning from the time when the tunable command is applied to the tunable device (304 ) 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 may be a value between 0 and 100, 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 input, the Y value is automatically calculated, and when the tunable device is used from the measurement value using the tuning time and the specific wavelength variable time grade of the system The allowable margin can be automatically calculated to some extent.

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.

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 channel 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.

4 is an exemplary block diagram illustrating a test-setup used for wavelength channel tuning time measurement of a wavelength tunable optical transmitter in accordance with an embodiment of the present invention.

The reference optical filter, described hereafter, must reflect the wavelength channel of the system in which the tunable device will be used.

4 (a) illustrates a case in which two optical filters 404 and 407 are used as reference filters. The center wavelength of the reference light filters 404 and 407 can be changed, and it should be set according to the condition to be measured. That is, if the center wavelength of one of the two reference light filters is aligned to the starting wavelength channel, the center wavelength of the other reference light filter must be tuned to the wavelength of the target channel. The photoelectric conversion efficiency or responsivity of the O / E converters 405 and 408 must be the same. If the photoelectric conversion efficiency is different, the measurement result should be corrected to determine the wavelength tuning time.

In this case, the power for the two wavelengths is summed (410), and then the wavelength channel tuning time is measured. At this time, the attenuator 402 is used for preventing overload of the O / E converters 405 and 408 and may be disposed on any optical path between the DUT 401 and the O / E converters 405 and 408 have.

4B is a test setup that can measure the tunable time of a tunable optical transmitter using one or more optical filters 413 as reference filters. In the case of a single reference optical filter, the center of the reference optical filter The wavelength should be adapted to the target wavelength channel.

4C is a test setup using two optical filters 1 and 2 (426 and 427) as a reference optical filter. The center wavelength of the reference optical filter can be changed and set according to the condition to be measured. That is, if the center wavelength of one of the two reference light filters is aligned to the starting wavelength channel, the center wavelength of the other reference light filter must be tuned to the wavelength of the target channel. 4C shows a structure using a 1: 3 optical splitter 422 so as to confirm whether the optical output is constant when the operating wavelength of the wavelength variable optical transmitter to be measured is changed. At this time, the variable attenuator 423 is used for the purpose of preventing overload of the O / E converter 424 and can be omitted.

4 (d) is a test setup using a structure in which AWG is connected in two stages (432, 433) as a reference optical filter. Here, since the 1: N connection can be established, the AWG has an advantage that it can selectively measure only the channel to be measured. That is, it is possible to measure the tuning time of the tunable optical transmitter 431 after forming connection relationships of various AWGs.

Figure 4 (e) is a test setup using an Etalon filter 442 as a reference light filter.

5 is a block diagram showing a test setup for receiving wavelength variable time measurement when the object to be measured is a wavelength variable optical filter. In this case, one or more optical transmitters may be used as reference optical transmitters. If only one optical transmitter is used as the reference optical transmitter, the output wavelength of the reference optical transmitter must be matched to the target operating wavelength of the wavelength tunable optical filter to be measured. If two optical transmitters are used as reference optical transmitters, the output wavelength of one of the reference optical transmitters is matched to the start wavelength channel of the DUT and the output wavelength of the other reference optical transmitters is matched to the target wavelength channel of the DUT . If a wavelength tunable optical transmitter is used as a reference optical transmitter, the wavelength tunable time must be shorter than that of the DUT.

As a result, the DUT illustrated in FIGS. 4 and 5 may include a tunable optical transmitter, a tunable optical filter, or a tunable optical filter. In the embodiment illustrated in FIGS. 4 and 5, It is only an example of various optical devices for measuring the tuning time and if the tuning time measuring method of the present invention is used, classifying the measured tuning time into classes for various optical devices is naturally within the scope of the present invention It can be seen as belonging to.

6 is a block diagram illustrating a wavelength channel tuning time measuring system of a tunable device according to another embodiment of the present invention.

The wavelength channel tuning time measuring system of the tunable device shown in FIG. 6 may have a configuration in which independent separate components are connected to various networks, while a separate component may constitute a single device.

Referring to FIG. 6, a wavelength channel tuning time measuring system according to an embodiment of the present invention includes a reference optical filter set 602, a photoelectric converter 603, a waveform monitor 604, and a controller 605, do.

The optical filter set 602 consists of a combination of reconfigurable optical filters. The center wavelength of each optical filter constituting the optical filter set 602 can be tunable, and it can be set according to the conditions to be measured.

The optical filter set 602 has at least two pass bands within a tuning range of the optical element 601 to be measured. The transmission loss of each optical filter constituting the optical filter set 602 should be normalized in a wavelength band of interest. Here, the optical filter set 602 should reflect channel spacing and spectra excursion characteristics of a specific network.

The photoelectric converter 603 is disposed between the optical filter set 602 and the waveform monitor 604 and outputs the light intensity output from the optical filter set 602 to an electrical Converts to intensity.

The photoelectric converter 603 may include at least one low-pass filter, and the bandwidth of the low-pass filter preferably has a value between DC and 10 * (1 / T _tr ) Hz . Here, T _tr denotes the time at which the output wavelength of the tunable device to be measured moves.

The maximum input light intensity acceptable in the photoelectric converter 603 is preferably 10 times or more the intensity of light output from the tunable device to be measured. Although not shown in FIG. 6, various kinds of attenuators may be used The intensity of the light output from the tunable device 601 may be adjusted before being applied to the photoelectric converter 603.

The waveform monitor 604 displays the intensity of the light converted into the electric signal output from the photoelectric converter 603 on the waveform monitor. Here, the waveform monitor 604 may have the same function as the oscilloscope, and stores the signal output from the photoelectric converter 603. [

The waveform monitor 604 may also store a signal transmitted from the control unit 605, which will be described later, and display the signal on the waveform monitor. At this time, the waveform monitor 604 can display at least two input signals, and monitors changes in the output waveform over time.

For example, the signal transmitted from the controller 605 and the signal transmitted from the photoelectric converter 603 can be simultaneously displayed on the waveform monitor 604, and the waveforms of the two signals can be monitored over time. Here, the signal transmitted from the controller 605 may be a wavelength change control signal for changing the wavelength of the tunable device 601.

The control unit 605 generates a wavelength variable command for changing the wavelength of the tunable device 601. [ Here, the wavelength tuning command may have the form of a control message for changing the wavelength to the target wavelength, or may have a direct current / voltage form.

The control unit 605 also controls the wavelength tuning of the tunable device 601 based on the waveform of the wavelength variable command signal stored and monitored in the waveform monitor 604 and the signal output from the photoelectric converter 603, Calculate the time.

An operation process for measuring the wavelength channel tuning time of the tunable device 601 by the wavelength channel tuning time measuring system according to the embodiment of the present invention will be described below.

First, the control unit 605 generates a wavelength variable command for changing the wavelength of the tunable device 601. Thereafter, the generated tunable command is applied to the network-connected tunable device 601, and the tunable device 601 starts the wavelength channel change to the target wavelength based on the transmitted tunable command.

The optical signal output from the tunable device 601 is applied to the optical filter set 602 and allows only the wavelength of the predetermined band to pass through the optical filter set 602 in the applied output optical signal. Here, the applied output optical signal means a signal in which the wavelength channel is changed from the tunable device 601 to the target wavelength, and the optical filter set 602 is set to pass only the target wavelength channel band.

The optical signal of the target wavelength channel passing through the optical filter set 602 is applied to the photoelectric converter 603, and the photoelectric converter 603 converts the optical signal of the input target wavelength channel into an electrical signal.

The optical signal of the target wavelength channel converted into the electrical signal by the photoelectric converter 603 is transmitted to the waveform monitor 604, and the waveform monitor 604 stores and displays the electrical signal of the input target wavelength channel. do.

Meanwhile, the wavelength variable command generated by the controller 605 is transmitted to the waveform monitor 604 through the network, and the waveform monitor 604 stores the wavelength variable command together with the electrical signal of the target wavelength channel And display.

Fig. 7 shows an exemplary result of measuring a change in light intensity with a change in wavelength. 7 (a) shows the result of the waveform monitor 604 showing a change in the light intensity according to the wavelength change, and Fig. 7 (b) / RTI >

Referring to FIG. 7, the controller 605 calculates a wavelength channel tuning time. The controller 605 calculates a time point at which the maximum output power of the wavelength tuning command becomes Z% (for example, 10% It is determined as the starting point for calculating the channel tuning time. Here, the determined starting point is regarded as a point in time when the tunable command is applied to the tunable device 601.

The control unit 605 waits until the time when the change of the light intensity according to the wavelength change converges for more than a predetermined time, and then reaches a point where Y% (e.g., 90%) of the maximum light intensity after the convergence It is determined as the ending point for calculating the wavelength channel tuning time. The wavelength channel tuning time can be calculated as the difference between the determined end point and the starting point.

The wavelength channel tuning time can be expressed as a time index measurable by the waveform monitor 604 as follows.

At this time, 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 be changed. When the wavelength change command is issued to the tunable device Refers to the time from the point in time at which the light intensity of the original wavelength before the wavelength change is changed to the point at which Y% begins to occur.

T _c is the time it takes for the change in measurable light intensity in the wavelength division multiplexed (WDM) channel to change to begin to stabilize within Y% of the final light intensity, and after the wavelength is changed to the target wavelength, Refers to the time from the start of Y% (for example, 90%) of the maximum light intensity to the end of Y% of the maximum light intensity when converged for a preset predetermined time or more.

T _tr is the time for the output wavelength of the tunable device to move from the time after Tp to the time before Tc

Meanwhile, the wavelength channel tuning time measuring system of the tunable device according to the embodiment of the present invention has two input ports (first input port, second input port) connected to the tunable device 601 to be measured .

Here, the first input port directly connects the tunable device 601 and the optical filter set 602, and the second input port connects the tunable device 601 and the photoelectric converter 603 Directly connect.

On the other hand, the wavelength channel tuning time measuring system according to the embodiment of the present invention may further include a switch 607 that can be electrically on / off controlled at the front end of the optical filter set 602 The tunable device 601 and the optical filter set 602 and the photoelectric converter 603 can be selectively connected according to the operation of the switch 607. [ For example, when the switch 607 is turned on, the tunable device 601 is directly connected to the optical filter set 602, and when the switch 607 is turned off, Lt; RTI ID = 0.0 > 603 < / RTI >

The selective connection of the tunable device 601 to the optical filter set 602 or the photoelectric converter 603 is intended to ensure the reliability of the wavelength channel tuning time measurement of the tunable device 601 .

For example, in order to measure a reliable wavelength channel tuning time, it is necessary that the property of the tunable device 601 to be measured is kept constant or the performance required by the photoelectric converter 603 is constantly displayed.

In order to secure the property of the tunable device 601 and the performance of the photoelectric converter 603 as described above, an initial setting for measuring the wavelength channel tuning time is required.

The initialization process according to an embodiment of the present invention is as follows.

First, the tunable device 601 is connected to the second input port, or the switch 607 is directly connected to the photoelectric converter 603.

Next, the controller 605 generates a wavelength variable command for changing the wavelength of the tunable device 601. [ Thereafter, the generated tunable command is applied to the network-connected tunable device 601, and the tunable device 601 starts the wavelength channel change to the target wavelength based on the transmitted tunable command.

The optical signal changed to the wavelength channel by the target channel is applied to the photoelectric converter 603 without passing through the optical filter set 602 and the optical signal is converted into an electrical signal and output to the waveform monitor 604. [

If the property of the tunable device 601 is maintained constant and the performance required by the photoelectric converter 603 is constantly displayed, the waveform of the signal output to the waveform monitor 604 is converged .

If the waveform of the signal output to the waveform monitor 604 does not converge after a predetermined time, it means that the tunable device 601 or the photoelectric converter 603 does not operate normally.

The wavelength channel tuning time measurement is performed according to the measurement process described above when the waveform of the output signal converges after a predetermined time according to the process performed in the initial setting step, thereby ensuring the reliability of the measurement.

FIG. 8 is a diagram illustrating another example of a measurement result of a power versus a wavelength change for measuring a wavelength channel tuning time according to an embodiment of the present invention. Specifically, through experiments using a TEC-controlled DFB laser, And the waveform of the laser is obtained by measuring the tuning time according to the present invention.

Fig. 8 is a wavelength tuning diagram when 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 channel tuning time can be measured after normalizing and adjusting the one level before and after the wavelength tuning, it is possible to hold the wavelength command as the starting point when the wavelength command is applied to the tunable device without normalization and the tunable device performs measurement setup It is also possible to calculate the difference between the two as the tuning time by taking the point at which the measured value on the waveform 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 channel tuning time measuring device is configured to transmit the initial wavelength of the tunable device and also to transmit the final wavelength, a change in the optical intensity, which is caused by the wavelength variation with time, 8.

Unlike FIG. 3, which normalizes the power change over the wavelength, the case of FIG. 8 is not normalized. This result may be due to a difference in insertion loss depending on the wavelength of the optical filter set used in the measuring apparatus. However, when the tunable device changes the output intensity according to the wavelength, the measurement result can be obtained as shown in FIG. 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 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 a pulse generator is used, the voltage or current of the tunable device

If you want to use a control method that changes the output wavelength, prepare the measurement setup as shown in Figure 9a. 9B is a graph showing information for measuring the wavelength channel tuning time for an arbitrary output wavelength from the starting point of the control signal in the measurement setup of FIG. 9A.

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 how much voltage or current should be applied to the tunable device to move from the initial wavelength to the target wavelength, 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 as it is.

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. 9D is a graph showing information for measuring the wavelength channel tuning time for an arbitrary output wavelength from the starting point of the control signal in the measurement setup of FIG. 9C.

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

To determine the commands to be sent to the tunable device to move from the initial 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.

Check tuning class of tunable device with average tuning time.

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. 9F is a graph showing information for measuring the wavelength channel tuning time for an arbitrary output wavelength from the starting point of the control signal in the measurement setup of FIG. 9E.

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

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

Check tuning class of tunable device with average tuning time.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

10: OLT
20: ODN
30: ONU

Claims

CLAIMS 1. A classifying device for an optical tunable device having a tunable transmitter,
An optical filter combination capable of converting a change in a transmission wavelength of the optical tunable device into a change in optical output intensity;
At least one photoelectric converter for converting the optical output intensity change from the optical filter combination into an electrical signal; And
And a waveform monitor for monitoring a waveform of a signal converted into an electrical signal by the photoelectric converter,
Wherein a class of the optical tunable device is determined based on a wavelength channel tuning time of the optical tunable device.

The method according to claim 1,
Further comprising a control unit for issuing a wavelength channel change command to the optical tunable device.

3. The method of claim 2,
The controller may be a pulse generator capable of applying a direct current or voltage so that an output wavelength of the optical tunable device can be changed or a step signal And the class discriminating device of the optical tunable device.

3. The method of claim 2,
The wavelength channel tuning time is defined as a time from when the wavelength change command is issued by the control unit to when the waveform of the signal displayed on the waveform monitor stably starts staying on the target WDM channel Characterized in that said optical tunable device comprises:

5. The method of claim 4,
Wherein the wavelength tuning time is (T _p or T _l ) + T _tr + T _c .
(T _p or T _l ) is a processing time or a latency time for controlling the output wavelength of the optical tunable device to be changed, T _c is a wavelength of the target wavelength division multiplexed (WDM) channel , And T _tr is the time from the time after Tp to the time before Tc)

The method according to claim 1,
Wherein the optical tunable device has a constant temperature function.

The method according to claim 1,
Wherein the optical tunable device is provided in an OLT or ONU of a passive optical communication network system.

The method according to claim 1,
Wherein the electrical signal is a value for a power change before the wavelength channel changes and after the wavelength channel changes.

1. A class classifier for an optical tunable device having a tunable receiver,
At least one reference transmitter capable of transmitting an optical signal of a predetermined wavelength to the optical tunable device;
At least one photoelectric converter that is transmitted by the reference transmitter and converts the optical signal received by the optical tunable device into an electrical signal; And
And a waveform monitor for monitoring a waveform of the optical signal converted into the electrical signal,
Wherein the class of the optical tunable device is determined by comparing a result monitored by the waveform monitor with a predetermined tunable mask.

10. The method of claim 9,
Further comprising a control unit for issuing a wavelength channel change command to the optical tunable device.