KR101491815B1 - Optical communication wavelength analyzer - Google Patents

Abstract

Disclosed is a wavelength analyzer for optical communications in which a wavelength error measuring unit and a channel information measuring unit are optically connected from an optical signal input unit. The wavelength error measuring unit and the channel information measuring unit are separately configured in different modules to be connected to the optical signal input unit individually and optically, or are integrally configured in one module to be optically connected to the optical signal input unit, wherein the wavelength error measuring unit outputs an error between the wavelength of an input optical signal and an ITU wavelength grid, and the channel information measuring unit outputs ITU wavelength channel information corresponding to the wavelength of an input optical signal. The wavelength analyzer for optical communications includes a reflecting type wavelength-variable filter or a transmitting type wavelength-variable filter, thereby outputting individual wavelength information even when a plurality of DWDW wavelengths are inputted at the same time.

Description

[0001] The present invention relates to an optical communication wavelength analyzer,

The present invention relates to a wavelength analyzer for optical communication capable of extracting wavelength information of an optical signal in a dense wavelength division multiplexing (DWDM) optical communication network. A wavelength error measuring unit for outputting an error between the wavelength of the optical signal input from the optical signal input unit and the ITU wavelength grid; and a wavelength error measuring unit for measuring an ITU wavelength corresponding to the wavelength of the input optical signal, The wavelength error measuring unit and the channel information measuring unit may be separately configured in different modules so that the optical signal input unit may be separately provided with the optical signal input unit, And the optical signal input means includes a reflective wavelength tunable filter or a transmission type tunable filter so that even when a plurality of DWDM wavelengths are input simultaneously, There is provided a wavelength analyzer for optical communication capable of outputting wavelength information.

The DWDM optical transmission system transmits and receives multiple wavelengths through a single optical fiber at the same time, which enhances the use efficiency of the optical line and is advantageous for large-capacity data transmission. With the development of optical device technology, an optical transceiver capable of transmitting 40 Gbps per wavelength has been commercialized as well as a 10 Gbps optical transceiver per wavelength.

The wavelengths used in DWDM optical transmission systems are usually within the C-band of 1,528 nm to 1,562 nm and the L-band of 1,570 nm to 1,605 nm, and the channel spacing is divided into 100 GHz, 50 GHz and 25 GHz in each wavelength band Is used. Wavelength values in vacuum are strictly defined by ITU-T as an international standard. Typical wavelengths used in 100GHz DWDM optical transmission equipment are 40 channels, and 50GHz DWDM optical transmission equipment can be expanded to 80 channels. Therefore, in case of transmitting 40 Gbps per wavelength, a 100 GHz 40-channel optical transmission equipment can transmit a capacity of 1.6 Tbps per optical fiber and a 50 GHz 80-channel optical transmission equipment can transmit a large capacity traffic of 3.2 Tbps per optical fiber.

In this way, wavelength resources in DWDM optical transmission networks are one of the main parameters that determine long term reliability and stability of optical transmission performance as well as optical transmission capacity and performance. If the wavelength of the optical signal deviates from the wavelength grid specified by the ITU-T and there is a problem in the transmission of the optical channel, the large-capacity DWDM optical transmission network may be used as a backbone or a backhaul, Resulting in serious conditions such as transmission failure or transmission failure. Therefore, the oscillation wavelength of the DWDM light source used in the DWDM optical transmission network and the center wavelength of the various types of DWDM optical filters installed are strictly controlled.

Examples of the DWDM optical filter include an array grating waveguide (AWG) filter, a thin-film filter (TFF), a wavelength band separation filter, an optical add / drop multiplexer (OADM), a fiber grating filter . The channel center wavelength of the optical filter should be within the tolerance range of the wavelength grid defined in ITU-T. In DWDM transmission networks, the error between the ITU-T wavelength grid and the center wavelength of the optical filter should be less than 1/10 of the channel spacing. For example, for a DWDM transmission network with 100 GHz wavelength spacing, the error of the center wavelength of the optical filter is ± 40 pm and for a DWDM transmission network with 50 GHz wavelength spacing is ± 20 pm.

In addition, the wavelength of the DWDM laser diode light source varies depending on the environmental temperature, the driving current, and the self-deterioration of the indium phosphide (InP) material, which may cause serious problems in the optical transmission performance. For example, when a distributed feedback laser (DFB laser) diode light source is used as a DWDM light source, the oscillation wavelength is about 0.1 nm per 1 degree of ambient temperature, and the oscillation wavelength per 1 mA of driving current is about 0.01 nm Is known to change. It is known that the change of the oscillation wavelength due to the deterioration of the InP material itself depends on the material composition, the exposure environment, the driving condition, and the use time. Therefore, the wavelength value of the optical signal emitted from the DWDM light source used in the optical transmission equipment should be monitored in real time, and the wavelength resource should be allocated, managed, and operated on the upper level of the optical transmission equipment. The wavelength stability of the DWDM source wavelength usually requires within 1/5 of the used wavelength channel spacing based on the end-of-life (EOL). As an example, the wavelength stability at a wavelength interval of 100 GHz is ± 0.1 nm, and the wavelength stability at 50 GHz is ± 0.05 nm.

The optical spectrum analyzer (OSA) having a spectrometer is a typical equipment for measuring the wavelength of an optical signal input / output from the DWDM optical transmission network. The wavelength resolution is 20 pm in the wavelength band from 1,260 nm to 1,650 nm Technology is mature enough to support commercial products. However, it is practically difficult to be mounted in a portable or optical transmission equipment system line card due to power consumption problem, volume problem, weight problem, high-cost problem, and restriction of temperature of use environment.

In order to overcome this problem, the proposed structure is a wavelength locker module. It is a module that detects wavelength error by emitting wavelength offset information relative to the ITU-T wavelength grid closest to the input light wavelength instead of emitting the absolute value of the input light wavelength.

FIG. 1 schematically shows a structure of a conventional wavelength locked module.

The structure of the conventional wavelength locked module 10 will be described with reference to this drawing.

A tap filter 105 is provided on the optical path 103 to be emitted from the collimator 102 connected to the optical fiber 101 and a first photodetector The etalon filter 106 and the second photodetector 107 to which the optical signal passing through the tap filter 105 is inputted are provided on the same optical path while the thermoelectric element 108 is provided as the temperature stabilizing means, And a temperature sensor 109 are mounted.

The DWDM optical signal input through the optical fiber 101 is input into the wavelength locked module 10 through the collimator 102 and is incident on the tap filter 105 installed on the optical path 103. A part of the optical signal incident on the tap filter 105 is reflected and input to the first photodetector 104 and photoelectrically converted to generate a first photodetection current and the remaining optical signal passing through the tap filter 105 is Passes through the etalon filter 106, enters the second photodetector 107, and is photoelectrically converted to generate a second photodetection current.

2 is a wavelength diagram showing the operation principle of the conventional wavelength locking module 10 described above. As shown in this figure, the second photodetector PD2 emitted from the second photodetector 107 follows the transmission characteristic of the etalon filter 406 having a free spectral range (FSR) periodicity Goes. However, in order to solve the problem that the absolute value varies depending on the input optical signal, the value of the second photocurrent (PD2) as the T value is set to a value It is possible to obtain a wavelength having pure wavelength dependence, that is, a wavelength exhibiting transmission characteristics such as the etalon filter 406, without the input optical signal dependency.

Equation (1): T = PD2 / PD1

3 is a graph showing a state of extracting an error signal of a transmission characteristic wavelength in the etalon filter.

The maximum value T2 and the minimum value T1 of the transmission characteristic wavelength 310 are the same as the transmission characteristic wavelength 310 due to the fineness of the etalon filter 106, (Finesse), and the wavelength period value WC is also equal to the FSR of the etalon filter 106.

Letting the target ITU-T wavelength grid value be l (i) in FIGS. 2 and 3, the transmission maximum wavelength value l (p) and the transmission minimum wavelength value l (q) of the etalon filter 106, The wavelength locking module 10 (i) is adjusted by adjusting the light incident angle [theta] of the etalon filter 106 so that l (i) ). ≪ / RTI >

The wavelength offset WO of the input wavelength value l (s) and the target ITU-T wavelength grid value l (i) is determined by the T graph value Ts corresponding to the input wavelength value l (s) (T) corresponding to the ITU-T wavelength grid 1 (i) and the T graph value Tref corresponding to the ITU-T wavelength grid 1 (i). If the input wavelength l (s) is present within the linear wavelength range G3 except for the first nonlinear section G1 near the transmission minimum wavelength value l (q) and the second nonlinear section G2 near the transmission minimum wavelength l (q) The magnitude of the wavelength error signal S3 and the magnitude of the wavelength offset WO are linearly proportional to each other so that the wavelength error information can be inferred.

The performance of the 50 GHz wavelength locked module 10 in a product in which the wavelength locked module 10 of FIG. 1 is commercialized is characterized in that the precision of the wavelength offset WO is about 10 to 25 pm and the linear wavelength range G3 is about 0.25 to 0.4 nm to be. It is also possible to apply the ITU-T wavelength grid of the entire C-band wavelength band or the ITU-T wavelength grid of the entire C + L band as well as the specific ITU-T wavelength grid using the periodicity of the etalon filter .

The structure of the wavelength locked module 10 is a structure using collimated light in free space. However, the same function can be configured using a flat waveguide. US Pat. No. 8,532,441 Optical device for wavelength locking uses a planar silicon-on-insulator (SOI) waveguide structure. A wavelength-locked module 10 uses a filter corresponding to a talon filter 106 A waveguide ring resonator structure is used as the waveguide ring resonator and a waveguide 1x2 optical splitter structure is used as a filter corresponding to the tap filter 105 to implement the wavelength locking function.

That is, the basic construction block and the operation principle for implementing the wavelength locking function are the same, but there is a difference in the detailed implementation method.

However, the conventional wavelength locked module 10 has two problems. First, there is a problem that applies only when there is only one input DWDM wavelength. In other words, there is a limitation in extracting the wavelength offset information from the target ITU-T wavelength grid only in the case of a single DWDM optical signal. In fact, DWDM optical transmission networks use up to 40 channels for 100 GHz wavelength spacing and up to 80 channels for 50 GHz wavelength spacing. Therefore, when a plurality of optical wavelengths are mixed and input to the conventional wavelength locking module 10, it is impossible to extract wavelength offset information with respect to the corresponding ITU-T wavelength grid for each wavelength.

Second, there is a problem that the absolute value of the input light wavelength can not be known when a single light wavelength is input. That is, you can see the wavelength offset relative to the ITU-T wavelength grid, but there is no way to know which ITU-T wavelength grid you are using. Due to the above problems, the wavelength locked module 10 is mainly used as means for stabilizing only one DWDM light source wavelength.

An optical wavelength power meter capable of measuring an optical signal by DWDM wavelength is disclosed in Korean Patent No. 10-1089182. Fig. 4 shows the structure of such an optical wavelength power meter. Referring to this figure, the optical wavelength power meter comprises an optical wavelength meter 810, an optical detecting device 803 and a driving means 806.

The optical wavelength measuring device 810 includes an input waveguide 801, a waveguide grating 802 and an output waveguide 807 formed on a flat waveguide substrate 800. The optical detecting device 803 is a single- And a photodetector 805. The driving means 806 is configured to move the photodetecting device 803 in a mechanical manner.

In this optical signal measuring device, when multiple DWDM light wavelengths are input to the input waveguide 801 and passed through the waveguide grating filter 802, the optical signal measuring device is outputted for each wavelength through the output waveguide 807 corresponding to each wavelength. At this time, light is incident on the optical detecting device 803 including the optical fiber 804 and the optical detector 805 to measure the optical signal. The driving device 806 is connected to the optical detecting device 803, The optical signal emitted from each exit waveguide 807 can be measured for each wavelength by moving the optical detecting device 803. [

In this structure, even when a multi-wavelength is input, the optical signal for each wavelength can be measured, thereby overcoming the problems of the conventional wavelength locking module. However, the wavelength accuracy is determined by the range of the 3-dB pass bandwidth of the waveguide grating filter, and typically has a bandwidth of 0.3 to 0.6 nm for the 100 GHz waveguide grating filter and 0.15 to 0.3 nm for the 50 GHz wavelength. There is a problem that the wavelength precision is insufficient to judge whether or not the optical wavelength signal to be used satisfies the wavelength stability requirement of 0.1 nm or less. Thus, there is a limit to be used for measuring an optical signal inputted within the range of the assigned DWDM channel wavelength without using it for precisely measuring the wavelength information.

U.S. Pat. No. 8,532,441 Korea Patent No. 10-1089182

It is an object of the present invention to provide a wavelength offset measuring apparatus and a channel measuring apparatus in which a wavelength error measuring unit and a channel measuring unit are separated from each other or configured integrally with each other so that not only wavelength offset information relative to a target ITU- We propose a wavelength analyzer for optical communication that can extract input wavelength channel information by providing target ITU-T wavelength grid information.

In addition, even when DWDM multi-wavelength is input, wavelength channel information can be extracted for each input wavelength by providing ITU-T wavelength grid information as well as wavelength offset information for the corresponding ITU-T wavelength grid value We propose a wavelength analyzer for optical communication.

Technical features of the wavelength analyzer for optical communication to attain the object intended by the present invention include optical signal input means having at least two output terminals; A tap filter that receives and reflects a part of the optical signal while receiving an optical signal emitted from a collimator optically connected to an output terminal of the optical signal input unit; and a first photodetector that receives a part of the optical signal reflected from the tap filter And an etalon filter provided on the optical path of the optical signal transmitted through the tap filter and a second optical receiver, and which measures a wavelength error of the wavelength of the input optical signal and an error signal between the ITU wavelength grid Wealth; A linear transmission filter that receives and reflects a part of the optical signal while receiving an optical signal outputted from a collimator optically connected to the other output terminal of the optical signal input unit; and a third transmission unit that receives a part of optical signals reflected by the linear transmission filter. And a fourth photodetector to which the optical signal transmitted through the linear transmission filter is input, and outputs the ITU channel information signal corresponding to the wavelength of the inputted optical signal.

The wavelength analyzer for optical communication has a structure in which the wavelength error measuring unit and the channel information measuring unit are separately formed as modules and optically connected to the optical signal input unit.

According to another aspect of the present invention, there is provided a wavelength analyzer for optical communication, comprising: optical signal input means having one output terminal; A tap filter for reflecting and transmitting a part of the optical signal while an optical signal outputted from a collimator optically connected to the optical signal input means is inputted; an etalon filter provided on the optical path of the optical signal transmitted through the tap filter; A wavelength error measuring unit for outputting an error signal to the ITU wavelength grid by the photocurrent output from the second photodetector; A linear transmission filter for receiving a part of the optical signal reflected by the tap filter of the wavelength error measuring unit to reflect and transmit a part of the optical signal, a third receiver for receiving the optical signal reflected from the linear transmission filter, And a channel information measuring unit for outputting the ITU wavelength channel information signal to the photocurrent outputted from the fourth photodetector through which the optical signal transmitted through the filter is incident.

The wavelength analyzer for optical communication has a structure in which the wavelength error measuring unit and the channel information measuring unit are formed of one module and are optically connected to the optical signal input unit.

The optical signal input means includes a light multiplexing branch in which a DWDM single wavelength optical signal is input.

In addition, the optical signal input means may include a light multiplexing branch in which a DWDM multi-wavelength optical signal is inputted, and a wavelength tunable control signal inputted from the outside, optically connected to the optical multiplexing branch, And a transmission wavelength tunable filter including a reflection type wavelength tunable filter that emits light in a wide-angle branch or a DWDM multi-wavelength optical signal is input, and a wavelength tunable control signal is applied to the tunable wavelength tunable filter to vary the transmission band center wavelength.

The wavelength analyzer of the present invention can accurately extract the input DWDM optical wavelength information by simultaneously emitting not only the ITU wavelength grid and the wavelength error information but also the ITU wavelength grid information for the DWDM single wavelength input optical signal, It is possible to accurately extract wavelength information for each wavelength by emitting not only the ITU wavelength grid and wavelength error information for each wavelength but also the corresponding ITU wavelength grid information for each wavelength, It can be applied to portable wavelength analyzer and it can be inserted into the line card of the optical transmission device to monitor the wavelength stability of the multi-wavelength DWDM optical signal in real time.

1 is a block diagram of a conventional wavelength locked module
FIG. 2 is a graph showing a current signal output from the wavelength locked module receiver of FIG. 1
3 is a graph showing the transmission characteristics of the etalon filter in the wavelength locked module of FIG.
4 is a block diagram of a conventional DWDM optical wavelength meter
5 is a block diagram of a wavelength analyzer according to a first embodiment of the present invention.
FIG. 6 is a graph showing the linear filter wavelength transmission and reflection characteristics in the present invention
7 is a graph showing a result of measurement of a wavelength information extracting signal using a linear filter in the present invention
8 is a graph illustrating the principle of ITU channel information extraction in the present invention
9 is a block diagram showing a wavelength analyzer according to a second embodiment of the present invention
10 is a block diagram showing a wavelength analyzer according to a third embodiment of the present invention
10A is a block diagram showing a wavelength analyzer according to a fourth embodiment of the present invention
FIG. 11 is a graph showing a wavelength tuning graph of the operation principle of the third embodiment and the fourth embodiment of the present invention.
12 is a graph showing the characteristics of the reflective wavelength tunable filter in the third embodiment of the present invention
13 is a block diagram showing a wavelength analyzer according to a fifth embodiment of the present invention
13A is a block diagram showing a wavelength analyzer according to a sixth embodiment of the present invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

The structure of the wavelength analyzer 20 according to the first embodiment of the present invention will be described with reference to FIG.

Referring to this figure, the optical splitter 300 includes a first output terminal 310 and a second output terminal 320 as optical signal input means and connected to the optical fiber 200, A wavelength error measuring unit 400 that is optically connected to the output terminal 310 and outputs an offset information signal based on a difference between the ITU-T wavelength grid value and the input DWDM wavelength value; And a channel information measurement unit 410 for outputting an ITU wavelength channel information signal optically connected to the wavelength 320 and closest to the inputted wavelength.

This structure is such that the optical splitter 300 has the first output 310 and the second output 320 so that the wavelength error measuring unit 400 and the channel information measuring unit 410 are separated into separate modules .

The optical branching branch 300 has a 1x2 or 2x2 optical distribution structure and is applied to a wavelength band transmission filter, a broadband optical filter, an optical switch, an optical isolator, a tap filter, an optical coupler, an optical splitter, and an optical amplifier .

The wavelength error measuring unit 400 may be applied to any conventional wavelength-locked module 10, a waveguide-type wavelength locked module, and other structures capable of performing wavelength locking. In the illustrated example, A first photodetector 404 for receiving a part of the optical signal reflected by the tap filter 405 to which the optical signal emitted from the collimator 401 optically connected to the first output terminal 310 is input and generating a first photodetection current, And an etalon filter 406 provided on the optical path of the optical signal passing through the tap filter 405 and a second photodetector 407 for generating a second photodetection current.

The channel information measuring unit 410 includes a linear transmission filter 411 to which an optical signal outputted from the collimator 402 connected to the second output terminal 320 of the optical splitter 300 is inputted, A third photodetector 413 for receiving a part of the reflected optical signal to generate a third photodetection current and a fourth photodetector 413 for receiving the optical signal transmitted through the linear transmission filter 411 to generate a fourth photodetection current 412) and a thermoelectric element 414 and a temperature sensor 415 as temperature sensing means for temperature stabilization.

The wavelength analyzer 20 configured as described above receives the DWDM single wavelength optical signal input to the optical fiber 200 into the optical splitter 300 and is output to the first output terminal 310 and the second output terminal 320.

The DWDM single wavelength optical signal output to the first output terminal 310 is input to the wavelength error measuring unit 400 through the collimator 401 and is incident on the tap filter 405. A part of the optical signal incident on the tap filter 405 is reflected and then input to the first photodetector 404 and photoelectrically converted to generate a first photodetection current I (1), which is incident on the tap filter 405 The remaining portion of the optical signal to be passed passes through the etalon filter 406 and is input to the second photodetector 407 and photoelectrically converted to generate a second photodetection current so that the target ITU-T wavelength grid value and the input DWDM wavelength And an offset information signal based on the difference from the value is output.

Meanwhile, the DWDM single wavelength optical signal output through the second output end 320 of the optical splitter 300 is input to the channel information measurement unit 410 through the collimator 402. The optical signal emitted from the collimator 401 is incident on the linear transmission filter 411 and partially reflected by the collimator 401 to be input to the third optical receiver 413 and photoelectrically converted to generate a third reception current, Is input to the fourth photodetector 412, and then photoelectrically converted to generate a fourth photocurrent, and the ITU wavelength channel information signal closest to the input wavelength is output.

An example of the transmission and reflection characteristics of the linear transmission filter 411 with respect to the input wavelength is shown in Fig. The transmission characteristic graph Tr is linearly decreased with respect to the input wavelength, and the reflection characteristic graph Re is linearly increased with respect to the input wavelength. If there is no self-loss in the linear transmission filter 411, the relation of the following equation (2) is established for all input wavelengths.

Equation (2): 1 = Tr (?) + Re (?)

Assuming that the optical coupling efficiency from the optical branch 300 to the third photodetector 413 is equal to the optical coupling efficiency to the fourth photodetector 412, the third photodetecting current and the fourth photodetecting current are given by the following equation (3) And Equation (4).

Equation (3): I (3)? Pinx (1-Tr (?))

Equation (4): I (4)? Pin x Tr (?)

Here, I (3) is a third photocurrent, I (4) is a fourth photocurrent, and Pin is an input optical signal value.

As an example of extracting the wavelength information in the C-band band for optical communication, a method of extracting the ITU channel information using the linear transmission filter 411 satisfying the following equation (5) will be described.

(5): Tr (?) = 0.9-0.8 占 (? -1530) / 50

In Equation (5),? Is a wavelength value in nm. Using the following equation (6) as an example of the wavelength information signal L (?),

L (?) = (I (4) -I (3)) / (I (4) + I (3)

The wavelength information signal L (λ) according to Equation (6) also shows a linear relationship with respect to wavelength since Tr (λ) exhibits linear characteristics with respect to wavelengths according to Equation (5). An example of the result of the wavelength information signal L (?) Measured by fabricating an actual device is shown in FIG.

A method for extracting ITU channel information from the channel information measurement unit 410 of FIG. 5 will be described with reference to FIG.

The graph 900 of the wavelength information signal L (?) According to Equation (6) decreases linearly with respect to the wavelength, and the value of L (i) corresponding to the ITU-T wavelength grid value? (I) Which is a constant value. L (i) is calculated by measuring L (s) corresponding to the input wavelength value (λ (s)) and finding L (i) whose absolute value of the difference with L (i) is less than the wavelength reference distance value (A) (I) corresponding to the input wavelength is an ITU-T channel corresponding to the input wavelength.

8, the magnitude of the difference between the L (R) value and the L (i) value corresponding to the wavelength? (R) that is smaller by 1/2 than the DWDM channel interval from? (I) Respectively. However, this is an example of one example, and the wavelength reference distance value A for extracting the wavelength channel information can be variously defined. In addition, the wavelength information extraction formula can be various forms other than the above-mentioned formula (6). For example, the following equations (7) to (9) are possible.

L (λ) = I (3) / I (4) α (1 / Tr (λ) -1)

L (?) = I (3) / (I (3) + I (4)

L (?) = I (4) / (I (3) + I (4)

Another embodiment of the wavelength analyzer proposed by the present invention will be described with reference to FIG. The wavelength analyzer 20a of this embodiment is a wavelength analyzer 20a in which a single wavelength optical signal is input as optical signal input means and the wavelength multiplexer 300a having one output stage 330 is explained with reference to the wavelength analyzer 20 The wavelength error measuring unit 400a and the channel information measuring unit 410a are integrated into a single package.

More specifically, the wavelength error measuring unit 400a is composed of a tap filter 405a, an etalon filter 406a, and a second light receiver 407a provided on the same optical path from the collimator 403, The unit 410a includes a linear transmission filter 411a, a third light receiver 413a and a fourth light receiver 412a to which a part of the signal reflected by the tap filter 405a is input, A temperature sensor 414a and a temperature sensor 415a are mounted.

In this embodiment, a DWDM single wavelength optical signal input to the optical splitter 300a through the optical fiber 200a is input into the wavelength analyzer 21a through the collimator 403 and is incident on the tap filter 405a. A part of the optical signal incident on the tap filter 405a is reflected and then reflected again by the reflection mirror 416 and input to the linear transmission filter 411a. A part of the optical signal incident on the linear transmission filter 411a is reflected again and input to the third photodetector 413a and photoelectrically converted to generate a fifth photodetection current and the remaining part of the incident optical signal is passed through a linear transmission filter Transmitted through the fourth photodetector 411a, input to the fourth photodetector 412a, and photoelectrically converted to generate a sixth photocurrent. On the other hand, the optical signal that is incident on the tap filter 405a and is not reflected is transmitted through the etalon filter 406a, input to the second light receiver 407a, and photoelectrically converted to generate a seventh optical signal.

The optical signal distribution of the tap filter 405a preferably has a reflectivity of 5 to 70% and a transmittance of 30 to 95%, the FSR value of the etalon filter 406a should not be larger than the DWDM wavelength channel spacing, And the Finesse value of the resin 406a is preferably 2 to 10.

The operation principle of the wavelength analyzer 21a is as follows.

The operation of extracting the ITU channel information using the fifth and sixth photocurrents is the same as that of the wavelength analyzer 20 described with reference to FIG.

Using Equations (3) and (4), Equation (10) is obtained.

Equation (10): I (5) + I (6)? Pin

Here, I (5) is a fifth light receiving signal, I (6) is a sixth light receiving signal, and Pin is an input optical signal.

The sum of the fifth light receiving signal I (5) and the sixth light receiving signal I (6) is linearly proportional to the input optical signal Pin. 3, which explains the operation principle of the conventional wave-locked module 10, the difference between the current received through the etalon filter 406a and the current received by the fifth photocurrent I (5) and the sixth photocurrent I (6 ) Can be used to extract the wavelength error information.

5 differs from the wavelength analyzer 20 of FIG. 5 in that the input optical signal information for extracting difference information between the input wavelength value and the target ITU wavelength grid value is transmitted through the etalon filter 406a, And the fifth photocurrent I (5) + the sixth photocurrent I (6).

Another embodiment of the wavelength analyzer proposed by the present invention will be described with reference to FIGS. 10 and 10A.

In this embodiment, as the optical signal input means, the reflection band center wavelength of the reflective wavelength tunable filter 500 is changed in order according to the variable wavelength control signal, and the reflection wavelength tunable filter 500 of the DWDM multi- Only the DWDM wavelengths present in the reflection bandwidth are selectively reflected. The selectively reflected DWDM wavelength is input to the wavelength error measuring unit 400 and the channel information measuring unit 410 as shown in FIG. 5 via the optical splitter 300b, Is input to the wavelength error measuring unit 400a and the channel information measuring unit 410a integrated into a single module as described and the DWDM wavelength information is sequentially output.

The wavelength analyzer 20b of the embodiment as shown in FIG. 10 includes a light dividing unit 300b for inputting a DWDM multi-wavelength optical signal as an optical signal input unit and a light dividing unit 300b for optically connecting the light dividing unit 300b to the light dividing unit 300b A reflection type wavelength tunable filter 500 that changes the center wavelength of the reflection band of an optical signal input from the optical splitter 300b and outputs the optical signal to the optical splitter 300b; A wavelength error measuring unit 400 and a channel information measuring unit 410 for outputting offset information as to the ITU wavelength as shown in FIG.

The optical multiplexing branch 300b includes a first output terminal 310a, a second output terminal 320a and an input / output terminal 340. The first output terminal 310a is optically connected to the wavelength error measuring unit 400, The output terminal 320a is optically connected to the channel information measurement unit 410 and the input and output terminal 340a is optically connected to the reflection type wavelength tunable filter 500. [

The reflective variable wavelength tunable filter 500 has a control port 501 and the center wavelength of the reflection band of the optical signal incident on the optical splitter 300b is varied by the wavelength variable control signal applied from the outside.

When the DWDM multi-wavelength optical signal is input to the optical splitter 300b through the input optical fiber 200b, the optical splitter 300b splits the inputted optical signal into a reflection wavelength variable signal through the input / And converts the optical path to the filter 500.

After that, the reflection wavelength tunable filter 500 changes the center wavelength of the reflection band of the optical signal as the tunable control signal is applied to the control port 607 from the outside, The wavelength error measuring unit 400 and the channel information measuring unit 410 are separated and input to the module housing through the first output 310a and the second output 320a.

The wavelength analyzer 20c of the embodiment as shown in FIG. 10A has a structure in which the optical splitter 300c and the reflection wavelength tunable filter 300c, in which the optical fiber 200c is optically connected as optical signal input means, And the output terminal 330a is provided with a wavelength error measuring unit 400a integrated into one module as shown in FIG. And the channel information measurement unit 410a.

The variable-wavelength fiber Bragg grating reflector may be applied to the reflective wavelength tunable filter 500. It is well known that the optical fiber bragg grating can easily change the reflection center wavelength by applying tensile or contraction pressure to the optical fiber grating by an external mechanical method. An example of the characteristics of a reflection type wavelength tunable fiber grating filter utilizing an optical fiber Bragg grating is shown in FIG. It has a different channel crosstalk rate of 25dB or more, a 3dB reflection bandwidth of 0.55nm, and a wavelength tunable range of about 30nm.

In addition to the wavelength tunable fiber Bragg grating reflector described above, it is also possible to use a wavelength variable filter using a diffraction grating and a reflective mirror, a wavelength tunable filter integrating a reflector on a Fabry-Perot wavelength tunable filter, a grating with a surface embossed on top of the flat waveguide And a variable wavelength filter using a thermo-optic effect, can be applied to various types of reflection type wavelength tunable filters.

The operation principle of the above-described wavelength analyzer 20b is shown in Fig. The reflection characteristic graph 502 of the reflective wavelength tunable filter 500 reflects only a specific DWDM wavelength band and transmits the others. The 3 dB reflection bandwidth G4 of the reflective wavelength tunable filter 500 is preferably 3/5 or less of the channel spacing DELTA lambda ch of the DWDM transmission network. In addition, the other-channel crosstalk rate B of the reflective variable wavelength tunable filter 500 is preferably 10 dB or more.

The wavelength analyzer 20c according to another embodiment of the present invention will be described with reference to FIG. 13 and FIG. 13A.

The wavelength analyzer 20d of the embodiment shown in FIG. 13 includes a transmission type wavelength variable filter 600 to which a DWDM multi-wavelength optical signal and a wavelength variable control signal are input as optical signal input means, 600, and outputs offset information to the ITU wavelength as described with reference to FIG. 5, and a channel information measurement unit 410.

The transmission type tunable filter 600 is optically connected to the optical fiber 200d and includes a control port 601 to which a tunable control signal is inputted and a first output terminal 602 and a second output terminal 603, The output terminal 602 is optically connected to the wavelength error measuring unit 400 and the second output terminal 603 is optically connected to the channel information measuring unit 410.

In this structure, a DWDM multi-wavelength optical signal is inputted to the transmission type variable wavelength filter 600 through the input optical fiber 200d and is separated into modules through the first / second output terminals 602 and 603, 400 and the channel information measurement unit 410. [

The wavelength analyzer 20d of the embodiment as shown in FIG. 13A has a transmission type wavelength tunable filter 600a optically connected to the optical fiber 200e, The output terminal 604 is optically connected to a module in which the channel information measuring unit 410a and the wavelength error measuring unit 400a are integrated as shown in FIG.

The transmissive wavelength tunable filters 600 and 600a are filters that transmit only a specific DWDM wavelength band. The wavelength tuning control signal is externally applied through the control ports 601 and 601a, thereby changing the center wavelength of the transmission band. The 3 dB transmission bandwidth of the transmission type tunable filter 600a is preferably 3/5 or less of the channel spacing DELTA lambda ch of the DWDM transmission network, and the other channel crosstalk rate is preferably 10 dB or more. The principle of extracting the wavelength information is the same as the principle of operation of the reflective wavelength tunable filter described above with reference to FIG.

A Fabry-Perot wavelength tunable filter may be applied to the transmission type tunable filters 600 and 600a. It is a known fact that the transmission center wavelength can be varied by adjusting the length of the Fabry-Perot cavity. Specifically, FP wavelength tunable filters using liquid crystals, Fabry-Perot wavelength tunable filters using PZT (piezo-electric transducer), Fabry-Perot wavelength tunable filters using micro electro mechanical systems (MEMS) A Fabry-Perot wavelength variable filter, and the like can be applied. In addition, various types of transmission type tunable filters such as a tunable wavelength tunable filter changing the incident angle to a dielectric multilayer thin film filter and a wavelength tunable filter using a thermo-optic effect in a planar waveguide mugginter interferometer structure can be used.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

20, 20a, 20b, 20c, 20d and 20e: wavelength analyzer
200, 200a, 200b, 200c, 200d, 200e: optical fiber
300, 300a, 300b, 300c: optical distributor
30, 310a: first output stage 320, 320a: second output stage
330: Output stage 340: I / O stage
400, 400a: wavelength error measuring unit 410, 410a: channel information measuring unit
401, 402, 403: collimator 404: first photodetector
405, 405a: tap filter 406, 406a: etalon filter
407, 407a: second photodetector 411, 411a: linear transmission filter
413, 413a: third photodetector 412, 412a: fourth photodetector
414, 414a: thermoelectric element 415, 415a: temperature sensor
416: reflection mirror 500, 500a: reflection type wavelength tunable filter
600, 600a: transmission type wavelength tunable filter 601: control port
602: first output terminal 603: second output terminal
604: output terminal 900: graph of the wavelength information signal L (l)

Claims (10)

Optical signal input means having at least two output terminals;
A tap filter 405 for reflecting and transmitting a part of the optical signal while an optical signal outputted from the collimator 401 optically connected to the output terminal of the optical signal input means is input; And an etalon filter 406 and a second photodetector 407 provided on the optical path of the optical signal transmitted through the tap filter 405. The first photodetector 404 receives the signal, A wavelength error measuring unit 400 for outputting a wavelength of the input optical signal and an error signal between the ITU wavelength grid and the wavelength of the inputted optical signal;
A linear transmission filter 411 for reflecting and transmitting a part of optical signals while receiving an optical signal outputted from a collimator 402 optically connected to another output terminal of the optical signal input means, A third photodetector 413 receiving a part of optical signals and a fourth photodetector 412 receiving an optical signal transmitted through the linear transmission filter 411. The fourth photodetector 412 receives an optical signal corresponding to the wavelength of the input optical signal, And a channel information measuring unit (410) for outputting an information signal.
Optical signal input means;
A tap filter 405a which receives and reflects a part of the optical signal inputted from the optical signal emitted from the collimator 403 which is optically connected to the optical signal inputting means 405a and the optical path of the optical signal transmitted through the tap filter 405a, A wavelength error measuring unit 400a for outputting an error signal between the etalon filter 406a provided on the ITU wavelength grid and the ITU wavelength grid by the photocurrent output from the second photodetector 407a;
A linear transmission filter 411a that receives part of the optical signal reflected by the tap filter 405a of the wavelength error measuring unit 400a and reflects and transmits a part of the optical signal, And a fourth photodetector 412a to which the optical signal transmitted through the linear transmission filter 411a is incident, and a channel optical modulator 412a for outputting the ITU wavelength channel information signal, And a measurement unit (410a).
The wavelength analyzer for optical communications according to any one of claims 1 to 3, wherein the optical signal input means includes a multiplexer (300, 300a) for inputting a DWDM single wavelength optical signal.
The optical signal input unit according to any one of claims 1 to 3, wherein the optical signal input unit comprises a multiplexer (300b, 300c) for inputting a DWDM multi-wavelength optical signal, an optical multiplexer (300b, 300c) And a reflective wavelength tunable filter (500) for varying the center wavelength of the reflection band of the optical signal input from the optical splitter (300b) by the tunable wavelength variable control signal and then outputting to the optical splitter (300b) Wavelength analyzer.
The optical signal input unit according to any one of claims 1 to 4, wherein the optical signal input unit comprises a transmission type wavelength variable filter (600, 600a) in which a DWDM multi-wavelength optical signal is input and a wavelength tunable control signal is applied thereto, And a wavelength analyzer.
The optical signal input device according to any one of claims 1 to 3, wherein the optical signal input means comprises a wavelength band transmission filter for transmitting only a used wavelength band, an optical circulator, an optical switch, an optical isolator, a tap filter, an optical coupler, And an optical splitter optically connected to the optical fiber for transmitting the DWDM single wavelength optical signal selected from the amplifier.
4. A method according to any one of the preceding claims, wherein the linear transmission filter (411, 411a) comprises selecting from a dielectric multilayer thin film filter having linear transmission and reflection characteristics along the input wavelength in the input DWDM wavelength range Wavelength analyzer for optical communication.
3. The wavelength analyzer for optical communication according to any one of claims 1 to 3, wherein the etalon filter has an FSR value not larger than a DWDM channel interval and a finesse value of 2 to 10.
5. The reflective wavelength tunable filter (500) of claim 4, wherein the reflective wavelength tunable filter (500) includes a 3 dB reflective bandwidth of 3/5 or less of the DWDM channel spacing, a different crosstalk rate of 10 dB or more, and a wavelength tunable range greater than the DWDM wavelength band A wavelength analyzer for optical communication.
The transmission type tunable filter according to claim 5, wherein the transmission type tunable filter has a 3 dB transmission bandwidth of 3/5 or less of the DWDM channel spacing, a different channel crosstalk rate of 10 dB or more, and a wavelength tunable range larger than a used DWDM wavelength band Wavelength analyzer.

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