KR100387288B1 - Apparatus for measuring wavelength and optical power and optical signal-to-noise ratio of an optical signal in wavelength-division multiplexing optical communications - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the wavelength, light intensity, and optical signal-to-noise ratio of an optical signal in wavelength division multiplex optical communication. In particular, the wavelength division multiplexed optical signal and the natural emission light discrimination signal are separated and detected by different optical detectors, or by using a signal band reflected optical filter to measure the wavelength, light intensity and optical signal-to-noise ratio of the optical signal. And optical signal-to-noise ratio measurement accuracy.

According to the present invention, an optical amplification means for amplifying a wavelength division multiplexed optical signal and outputting natural emission light; Branching means for branching a predetermined portion of the output of the optical amplifying means; Band-pass optical variable filter means for scanning the wavelength of the output according to the control signal by the transmission wavelength; Optical rotating means for rotating the input and output of the optical signal clockwise; Reflecting means for reflecting only a specific wavelength component of the natural emission light and outputting a natural emission light discriminating signal; Optical / electric conversion means for converting the intensity of the received light into an electrical signal; Signal processing means for calculating the wavelength, the light intensity, and the optical signal-to-noise ratio of the optical signal by using the electrical signal and the control signal output from the optical / electric conversion means; An apparatus for measuring wavelength, light intensity, and optical signal-to-noise ratio of an optical signal in a wavelength division multiplex optical communication comprising the bandpass optical variable filter means and a control signal generating means for providing a control signal to the signal processing means Is presented.

Description

Apparatus for measuring wavelength and optical power and optical signal-to-noise ratio of an optical signal in wavelength-division multiplexing optical communications}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the wavelength, light intensity, and optical signal-to-noise ratio of an optical signal in wavelength division multiplex optical communication. More specifically, the present invention relates to a technique for measuring wavelength, light intensity, and optical signal-to-noise ratio of an optical signal in a wavelength division multiplex optical communication using a natural emission light discrimination signal and a bandpass optical variable filter.

Wavelength division multiplexing is one of the ways to increase the communication capacity of the existing optical fiber. In order to increase the stability of the wavelength division multiplex optical communication system, the optical network operator transmits each optical signal by measuring the wavelength, light intensity, and optical signal-to-noise ratio of each wavelength division multiplexed optical signal. The condition should be monitored.

1 is a graph showing an optical spectrum of an optical signal (optical signals a, b, c, d) in which four wavelengths are multiplexed using an optical spectrum analyzer having a conventional rotating diffraction grating.

As an example, the equation for the optical signal to noise ratio of the optical signal a is as follows.

Therefore, in order to measure the optical signal-to-noise ratio of the optical signal a, it is necessary to know the noise intensity included in the optical intensity of the optical signal a. However, since this is difficult, the noise intensity of a is approximated from the light intensity of the ambient wavelength of the optical signal a, and the optical signal-to-noise ratio of the optical signal a is measured therefrom.

Existing optical spectrum analyzers have the advantages of wide measurement range and high precision, while they are bulky and expensive, and therefore, they require a lot of cost and space for installation in multiple locations for WDM system monitoring. Difficulties follow

Recently, various methods have been proposed to compensate for the shortcomings of the optical spectrum analyzer. Among them, the wavelength division multiplexed light is relatively inexpensive using a small bandpass optical variable filter and an optical detector. Devices that measure the wavelength, light intensity, and optical signal-to-noise ratio of signals are in the spotlight.

FIG. 2 illustrates the wavelength and light intensity of a wavelength division multiplexed optical signal using a 2 × 1 optical switch, a broadband light source, a comb-shaped optical filter, and a bandpass optical variable filter to provide a reference wavelength according to the related art. A diagram showing an apparatus for measuring optical signal to noise ratio. This approach has been applied to products sold by the company MICRON OPTICS, INC., Located at 1900 Centry Place, Suite 200, Atlanta, Georgia 30345, USA.

Referring to FIG. 2, a portion of the wavelength division multiplexed optical signal is branched by the 1 × 2 optical coupler 202 and input to the 2 × 1 optical switch 204. As an example, an optical spectrum of a wavelength division multiplexed optical signal is shown in the figure. The broadband light source 208 outputs natural emission light having a wide range of wavelength components, and the comb-like optical filter 206 receives such natural emission light and passes only components of a comb-shaped specific wavelength string. Light passing through the comb-shaped optical filter 206 is input to the 2x1 optical switch 204. As an example, the light spectrum of the broadband light source 208 and the spectrum of light passing through the comb-shaped optical filter 206 are shown in the figure.

The switching state of the 2x1 optical switch 204 is determined by the switch regulator 216 and the light passing through the 2x1 optical switch 204 is input to the bandpass optical variable filter 210. The transmission wavelength of the bandpass optical variable filter 210 moves according to the control signal output from the control signal generator 214.

If the transmission wavelength of the bandpass light variable filter 210 is moved proportionally by a control signal which sequentially increases, the light passing through the bandpass light variable filter 210 is received by the photodetector 212 and is proportional to the light intensity. When converted into an electrical signal, an electrical signal having a shape similar to that of the light spectrum of the wavelength-division multiplexed optical signal or the light passing through the comb-shaped optical filter 206 according to the switching state of the 2 × 1 optical switch 204 is optical. It is output from the detector 212 along the time axis. The electrical signal output from the photo detector 212 is input to the signal processor 218 together with the switch control signal provided from the switch regulator 216 and the control signal provided from the control signal generator 214.

Next, look at the measuring principle of Figure 2 as follows. In the first step, the switching state of the 2 × 1 optical switch 204 is determined and maintained so that the light passing through the comb-shaped optical filter 206 can be input to the bandpass optical variable filter 210. The band pass light variable filter 210 scans the light passing through the comb-shaped light filter 206 according to the control signal applied thereto.

The signal processor 218 receives an electric signal similar to the spectrum of the light passing through the comb-shaped optical filter 206 from the photo detector 212 according to the scan time, and then finds the positions of the peaks of the electric signal and controls corresponding thereto. Find the magnitude of the signal. At this time, since the positions of the peaks are determined by the comb-shaped optical filter 206, it is known that the offset of the band pass optical variable filter 210 with respect to the control signal applied when measuring the wavelength of the wavelength division multiplexed optical signal. Is used to calibrate the value.

In the next step, the switching state of the 2x1 optical switch 204 is determined and maintained such that the wavelength division multiplexed optical signal is input to the band pass optical variable filter 210. As above, the bandpass optical variable filter 210 scans an optical spectrum of a wavelength division multiplexed optical signal according to an applied control signal. The signal processor 218 receives an electrical signal similar to the optical spectrum of the wavelength division multiplexed optical signal from the photo detector 212 according to the scan time, finds the positions of the peaks of the electrical signal, and then selects corresponding control signal values. Find out.

The wavelength of each wavelength division multiplexed optical signal is measured by referring to the offset value of the band pass optical variable filter 210 for the control signal measured in the previous step. In addition, the signal processor 218 measures the light intensity of the wavelength division multiplexed optical signal using the sensitivity of the light detector 212, and divides the wavelength from the light intensity of the peripheral wavelength of the wavelength division multiplexed optical signal. The optical signal to noise ratio of the multiplexed optical signal is measured.

However, this method requires a 2 x 1 optical switch and a broadband light source, which is an active optical device, and thus has a disadvantage of durability and stability.

3 is a view illustrating a wavelength division multiple coupler, a wavelength division demultiplexer, a reference light source providing a reference wavelength, and a wavelength and light intensity of a wavelength division multiplexed optical signal using a bandpass optical variable filter according to the related art. A diagram showing an apparatus for measuring optical signal to noise ratio. This approach has been applied to devices patented and sold by AXSUN Technologies Inc., located at 1 Fortuen Drive, Billerica, MA 01821, USA.

The reference light source 304 outputs light having a wavelength different from that of the wavelength division multiplexed optical signal, which is used to find the offset of the bandpass optical variable filter 308 for the control signal in a manner similar to that of FIG.

The measuring principle is as follows. The wavelength division multiplexed optical signal branched by the 1 × 2 optical coupler 302 is inputted to the wavelength division multiple coupler 306 together with the light output from the reference light source 304, and then merged into the band pass optical variable filter 308. Is entered. As an example, an optical spectrum of a wavelength division multiplexed optical signal is shown in the figure. The band pass light variable filter 308 scans the light output from the wavelength division multiple coupler 306 according to the applied control signal.

The light passing through the bandpass optical variable filter 308 is separated into a wavelength division multiplexed optical signal by the wavelength division demultiplexer 310 and the light output from the reference light source 304, and each of them is different from each other. , 314). The signal processor 316 receives the electrical signals output from the photo detectors 312 and 314 and measures the wavelength, the light intensity, and the optical signal-to-noise ratio of the wavelength-division multiplexed optical signal in a manner similar to that of FIG. 2.

In FIG. 3, unlike the method of FIG. 2, the wavelength division multiplexed optical signal and the light output from the reference light source 304 are simultaneously scanned, the wavelength division multiple coupler 306, the wavelength division demultiplexer 310, and a separate light. Since the detector 314 separates and detects the offset value of the band pass optical variable filter 308 for the applied control signal based on the light output from the reference light source 304 without using a 2 x 1 optical switch. It has the advantage of knowing. However, such a method also requires a reference light source, which is an active optical device, as in the method of FIG.

4 is a conventional technology invented to exclude the use of an active optical device, which is a disadvantage in FIGS. 2 and 3, and was presented at the seventh optoelectronic and optical communication conference on May 17, 2000 (Chu Kwang-wook, Park Geun-yeol, Sang Bae Lee, Yoon Je Oh, Chang Hee Lee, Sang Hee Shin, "A New Fiber Channel Analyzer for WDM Optical Communication," FC2-19P, pp. 293, 2000). This method does not use a light source, which is a separate active optical element, by using the natural emission light output from the optical amplifier which is essentially used to compensate for the loss of the optical fiber optical signal in the optical communication system. And the offset value of the bandpass optical variable filter for the applied control signal is obtained using only the inexpensive fiber Bragg grating.

Next, the measuring principle is as follows. The wavelength division multiplexed optical signal is input to the optical amplifier 402. In general, the optical amplifier 402 amplifies the wavelength division multiplexed optical signal and outputs natural emission light. As an example, when the optical amplifier 402 is an erbium-doped fiber amplifier, a wavelength spectrum multiplexed optical signal and an optical spectrum of spontaneous emission light are shown.

The light output from the optical amplifier 402 is branched by the 1 × 2 optical coupler 404 and input to two successive optical fiber Bragg gratings 408 and 410 through the 2 × 1 optical coupler 406. The optical fiber Bragg gratings 408 and 410 reflect the wavelength components corresponding to the grating periods among the input optical signals and pass the rest.

Therefore, the reflected light has a wavelength that matches the reflection wavelength of the optical fiber Bragg grating 408 and 410, and serves as a natural emission light discrimination signal used to determine the offset value of the band pass light variable filter 414 for the applied control signal. Do it. As an example, the light spectrum of the natural emission light discrimination signal and the remaining light spectrum in which the natural emission light discrimination signal part is omitted are shown in the drawing.

The spontaneous emission discrimination signal is branched through the 2 × 1 optical coupler 406 and input to the 2 × 1 optical coupler 412, while the luminous intensity 2 × 1 optical coupler passed through two successive optical fiber Bragg gratings 408 and 410. 412 is entered. In addition, the 2 × 1 optical coupler 412 sums the two inputted light beams, and when the natural emission light discrimination signal is summed more than the light passing through the two consecutive optical fiber Bragg gratings 408 and 410, as shown in FIG. 4. The spontaneous emission light discrimination signal appears in the spectrum of the light combined by the 2x1 optical coupler 412. The light output from the 2 × 1 optical coupler 412 is input to the bandpass optical variable filter 414, and the transmission wavelength of the bandpass optical variable filter 414 is changed according to the control signal output from the control signal generator 420. While scanning, the light output from the 2x1 optical coupler 412 is scanned.

If the transmission wavelength of the bandpass light variable filter 414 moves in proportion to the sequentially increasing control signal, the light passing through the bandpass light variable filter 414 is received by the photodetector 416 and is proportional to the light intensity. When converted into an electrical signal, an electrical signal similar in shape to the optical spectrum of the light output from the 2x1 optical coupler 412 is output from the photodetector 416 along the time axis. The electric signal output from the photo detector 416 over time is input to the signal processor 418 together with the control signal provided from the control signal generator 420. As an example, a graph of the electrical signal output from the photo detector 416 is shown in the figure.

The signal processor 418 finds and distinguishes a wavelength division multiplexed optical signal and a natural emission light discrimination signal that appear in the electrical signal input from the photo detector 416 with reference to the control signal. Since the wavelength of the natural emission discrimination signal coincides with the reflection wavelengths of the optical fiber Bragg gratings 408 and 410, the wavelength division multiplexing is performed from the wavelength of the natural emission discrimination signal by using the natural emission light discrimination signal on the time axis and the position information of the optical signal. The offset value of the band pass optical variable filter 414 for the control signal applied when the wavelength of each of the optical signals is measured may be corrected.

In addition, the signal processor 418 may measure the light intensity of the wavelength division multiplexed optical signal using the sensitivity value of the photo detector 416. In addition, by measuring the light intensity of the peripheral wavelength of the wavelength division multiplexed optical signal to measure the optical signal to noise ratio of the wavelength division multiplexed optical signal.

This method eliminates the light source, which is a separate active optical element, by using the natural emission light output from the optical amplifier, which is essentially used to compensate for the loss of the optical fiber signal in the optical communication system, and only the inexpensive optical fiber Bragg gratings 408 and 410 It is advantageous to find the offset value of the band pass optical variable filter for the applied control signal.

However, this method has a disadvantage in that the light intensity and measurement error of the optical signal-to-noise ratio are affected by the performance of the optical fiber Bragg grating.

If the wavelength division multiplexed optical signal is reflected besides the light used as the natural emission light discrimination signal in the optical fiber Bragg gratings 408 and 410, the reflected wavelength division multiplexed optical signal is divided into two optical fiber Braggs that are continuous in the 2 × 1 optical coupler 412. It is combined with the wavelength division multiplexed optical signal passing through the grating.

In this case, the wavelength division multiplexed optical signal reflected from the optical fiber Bragg gratings 408 and 410 and the wavelength division multiplexed optical signal passing through the optical fiber Bragg gratings are input to the 2 × 1 optical coupler 412 through different paths, thereby causing interference. . Therefore, in the case of constructive interference, the light intensity received from the photodetector becomes larger than the actual value, and in the case of destructive interference, the light intensity is smaller than the actual value, thereby causing a measurement error. As a result, errors occur in optical signal-to-noise ratio measurements.

Accordingly, the present invention is to solve the above problems, the present invention is to separate the wavelength division multiplexed optical signal and the natural emission light discrimination signal and to detect each of the different optical detectors or to use the signal band reflected optical filter wavelength of the optical signal The purpose of the present invention is to increase the accuracy of optical intensity and optical signal to noise ratio measurement by measuring the optical intensity and optical signal to noise ratio.

The present invention as a technical idea for achieving the above object

Optical amplifying means for amplifying a wavelength division multiplexed optical signal and outputting natural emission light;

Branching means for branching a predetermined portion of the output of the optical amplifying means;

A band pass optical variable filter means which transmits a wavelength according to a control signal and scans the output light of said branching means;

Optical rotating means for rotating the input and output of the optical signal clockwise;

Reflecting means for reflecting only a specific wavelength component of the natural emission light and outputting a natural emission light discriminating signal;

Optical / electric conversion means for converting the intensity of the received light into an electrical signal;

Signal processing means for calculating the wavelength, the light intensity, and the optical signal-to-noise ratio of the optical signal by using the electrical signal and the control signal output from the optical / electric conversion means;

An apparatus for measuring wavelength, light intensity, and optical signal-to-noise ratio of an optical signal in a wavelength division multiplex optical communication comprising the bandpass optical variable filter means and a control signal generating means for providing a control signal to the signal processing means Is provided.

1 is a graph showing the wavelengths and wavelengths of the wavelength-division multiplexed optical signals and the optical spectra of the optical signal-to-noise ratio shown on the output screen of the optical spectrum analyzer according to the related art.

FIG. 2 illustrates the wavelength and light intensity of a wavelength division multiplexed optical signal using a 2 × 1 optical switch, a broadband light source, a comb-shaped optical filter, and a bandpass optical variable filter to provide a reference wavelength according to a conventional technology. Figure showing a device for measuring optical signal to noise ratio

3 is a view illustrating a wavelength division multiple coupler, a wavelength division demultiplexer, a reference light source providing a reference wavelength, and a wavelength and light intensity of a wavelength division multiplexed optical signal using a bandpass optical variable filter. Figure showing a device for measuring optical signal to noise ratio

4 is a diagram illustrating an apparatus for measuring wavelength, light intensity, and optical signal-to-noise ratio of a wavelength division multiplexed optical signal using an optical fiber Bragg grating and a bandpass optical variable filter for providing a natural emission light discrimination signal according to the related art. Drawing

5 is a wavelength and light intensity of a wavelength division multiplexed optical signal using an optical circulator and a separate optical detector for detecting natural discriminating light according to an exemplary embodiment of the present invention, thereby eliminating interference between optical signals. And an apparatus for measuring an optical signal to noise ratio

FIG. 6 is a diagram illustrating wavelengths, optical intensities, and optical signals of a wavelength division multiplexed optical signal that reduces interference between optical signals using a signal-band reflection optical filter according to another embodiment of the present invention. Figure showing a device for measuring the noise ratio

<Explanation of symbols for the main parts of the drawings>

202,302,404,504,604: 1 × 2 optical coupler 204: 2 × 1 optical switch

206: comb-shaped optical filter 208: broadband light source

210,308,414,506,616: Bandpass Optical Variable Filter

212,312,314,416,514,516,618: Photo Detector

214,318,420,520,622: control signal generator 216: switch controller

218,316,418,518,620: Signal processor 304: Reference light source

306: wavelength division multiple coupler 310: wavelength division demultiplexer

402,502,602: optical amplifier 406,412: 2 x 1 optical switch

408,410,510,512,610,612: Fiber Bragg Grating

508,606: optical rotator 608: signal band reflection optical filter

614: optical terminator

Hereinafter, with reference to the accompanying drawings, the configuration and operation of the embodiment of the present invention will be described in detail.

FIG. 5 illustrates an apparatus for measuring a wavelength, an optical intensity, and an optical signal to noise ratio of an optical signal in a wavelength division multiplex optical communication according to an exemplary embodiment of the present invention.

5, an optical amplifier 502, a 1x2 optical coupler 504, a bandpass optical variable filter 506, an optical rotator 508, two optical fiber Bragg gratings 510 and 512, and two Photo detectors 514 and 516, a signal processor 518, and a control signal generator 520.

The optical amplifier 502 receives and amplifies a wavelength division multiplexed optical signal and outputs the same with natural emission light. At this time, as the optical amplifier 502, a rare earth-added optical fiber amplifier, a semiconductor optical amplifier, a Raman optical amplifier, or the like can be used.

The bandpass optical variable filter 506 may be a Fabry-Perot variable filter, an integrated optical device including a grating, a multilayer thin film device, an acoustic-optic filter, or the like.

The optical rotator 508 has three input / output terminals, and the input and output correspond to the clockwise direction. That is, when light is input to any terminal, it is always output to the next terminal in the clockwise direction. However, the same effect can be obtained by using a 2 x 1 optical coupler instead of the optical rotator 508.

The optical fiber Bragg gratings 510 and 512 reflect light of a wavelength corresponding to the grating period and pass light of the remaining wavelengths. In addition, only a specific wavelength component of the natural emission light is reflected to output a natural emission light discrimination signal. In this case, an integrated optical device including a grating may be used instead of the optical fiber Bragg gratings 510 and 512.

Next, the operation and effects of the device according to the present invention will be described.

The optical amplifier 502 receives and amplifies a wavelength division multiplexed optical signal and outputs the same with natural emission light. As an example, when the optical amplifier 502 is an erbium-doped fiber amplifier, the optical spectrum of the wavelength-division multiplexed optical signal and natural emission light amplified is shown in the drawing. The light output from the optical amplifier 502 is branched through the 1 × 2 optical coupler 504 and input to the band pass optical variable filter 506.

The transmission wavelength of the bandpass optical variable filter 506 scans the light output from the 1 × 2 optical coupler 504 while moving in accordance with the control signal output from the control signal generator 520.

Light passing through the bandpass optical variable filter 506 is input to two continuous optical fiber Bragg gratings 510 and 512 through the optical rotator 508. The optical fiber Bragg gratings 510 and 512 reflect light of a wavelength corresponding to the lattice period and pass the remaining wavelength components, and the reflected light serves as a natural emission light discrimination signal. The natural emission light discrimination signal generated by the optical fiber Bragg gratings 510 and 512 is received by the optical detector 516 through the optical rotator 508.

The remaining wavelength components, which are not reflected by two consecutive optical fiber Bragg gratings 510 and 512, are received by another photodetector 514. The two photo detectors 514 and 516 convert the light intensity of the received light into an electrical signal according to the scan time, respectively, and output the converted electrical signals, and the converted two electrical signals are combined with the control signal provided from the control signal generator 520 and the signal processor 518. ) Is entered.

The signal processor 518 locates the spontaneous emission light discrimination signal on the time axis of the electrical signal input from the photo detector 516. At this time, the wavelength of the natural emission determination signal is the same as the reflection wavelength of the optical fiber Bragg gratings (510,512).

The signal processor 518 locates the wavelength division multiplexed optical signal on the time axis of the electrical signal input from another photo detector 514. The offset value of the bandpass optical variable filter 506 for the control signal applied when the wavelength of each wavelength-divided multiplexed optical signal is measured using the position on the time axis of the natural emission light discrimination signal found above is corrected. Can be. In addition, the signal processor 518 measures the light intensity of the wavelength division multiplexed optical signal using the sensitivity value of the photo detector 514, and measures the light intensity of the peripheral wavelength of each wavelength division multiplexed optical signal. The optical signal to noise ratio of each multiplexed optical signal is measured.

In this method, optical intensity and optical signal-to-noise ratio measurement errors occur because the wavelength division multiplexed optical signal reflected from the optical fiber Bragg gratings 510 and 512 is not merged with the wavelength division multiplexed optical signal passed through the optical fiber Bragg gratings 510 and 512. I never do that.

In order to further increase the accuracy of the wavelength measurement, the optical rotator 508 and the optical detector 514 may include an optical fiber Bragg grating reflecting natural emission light between the wavelength division multiplexed optical signals in addition to the optical fiber Bragg gratings 510 and 512. In addition, the offset of the band pass optical variable filter with respect to the control signal can be found more accurately.

FIG. 6 illustrates an apparatus for measuring wavelength, light intensity, and optical signal-to-noise ratio of a wavelength division multiplexed optical signal according to a second embodiment of the present invention.

6, an optical amplifier 602, a 1x2 optical coupler 604, an optical rotator 606, a signal band reflected optical filter 608, two optical fiber Bragg gratings 610 and 612, and an optical The terminator 614, the bandpass optical variable filter 616, the photodetector 618, the signal processor 620, and the control signal generator 622 are comprised.

The optical amplifier 602 not only amplifies the wavelength division multiplexed optical signal but also outputs natural emission light. At this time, as the optical amplifier 602, a rare earth-added optical fiber amplifier, a semiconductor optical amplifier, a Raman optical amplifier, or the like can be used.

The optical rotator 606 has three input / output terminals, and the input and output correspond to the clockwise direction. That is, when light is input to any terminal, it is always output to the next terminal in the clockwise direction. However, the same effect can be obtained by using a 2 x 1 optical coupler instead of the optical rotator 606 described above.

The signal band reflection optical filter 608 reflects the wavelength of the wavelength division multiplexed optical signal band and passes the remaining band.

The optical fiber Bragg gratings 610 and 612 reflect light of a wavelength corresponding to the grating period and pass light of the remaining wavelengths. In addition, only a specific wavelength component of the natural emission light is reflected to output a natural emission light discrimination signal. In this case, as the optical fiber Bragg gratings 610 and 612, an integrated optical device including a grating may be used.

The optical terminator 614 completely extinguishes without reflecting the input light at all.

The bandpass optical variable filter 616 may be a Fabry-Perot variable filter, an integrated optical device including a grating, a multilayer thin film device, an acoustic-optic filter, or the like.

The actions and effects of the device according to the invention are as follows.

The optical amplifier 602 receives a wavelength-divided multiplexed optical signal, amplifies it, and outputs it with natural emission light. As an example, when the optical amplifier 602 is an erbium-doped fiber amplifier, the optical spectrum of the wavelength-division multiplexed optical signal and the natural emission light amplified is shown in the drawing.

Light output from the optical amplifier 602 is branched through the 1 × 2 optical coupler 604 and input to the signal band reflected optical filter 608 through the optical rotator 606. The portion of the light input from the optical rotator 606 included in the signal band is reflected by the signal band reflecting optical filter 608, and the rest is passed through as it is. As an example, the light spectra of the light reflected by the signal band reflecting optical filter 608 and the light passing through the signal band reflecting optical filter are shown in the drawings.

Light passing through the signal band reflected optical filter 608 is input to two successive optical fiber Bragg gratings 610 and 612. The optical fiber Bragg gratings 610 and 612 reflect the portion of the incoming light that matches the reflected wavelength of the optical fiber Bragg gratings 610 and 612 and pass the rest. At this time, the reflected light becomes a natural emission light discrimination signal. As an example, the remaining light spectrum from which the natural emission light discrimination signal is omitted is shown in the drawing. The signal passing through the optical fiber Bragg gratings 610 and 612 is input to the optical terminator 614. Since the optical terminator 614 does not reflect the input light at all, the light passing through the optical fiber Bragg gratings 610 and 612 is completely destroyed.

The spontaneous emission light discrimination signal reflected by the optical fiber Bragg gratings 610 and 612 merges with the light reflected by the signal band reflected light filter 608 after passing back through the signal band reflected light filter 608. As an example the light spectrum of the combined light is shown in the figure.

The combined light is inputted to the bandpass optical variable filter 616 through the optical rotator 606, and the transmission wavelength of the bandpass optical variable filter 616 is moved in accordance with the control signal output from the control signal generator 622. Scan the light output at 606.

If the transmission wavelength of the bandpass light variable filter 616 is moved proportionally by a control signal which sequentially increases, the light passing through the bandpass light variable filter 616 is received by the photodetector 618 and is proportional to the light intensity. When converted into an electrical signal, an electrical signal similar in shape to the optical spectrum of the light output from the optical rotator 606 is output from the photo detector 618 over time. The electrical signal output from the photo detector 618 is input to the signal processor 620 together with the control signal provided from the control signal generator 622. As an example a graph of the electrical signal output from the photodetector 618 over time is shown in the figure.

The signal processor 620 finds and distinguishes a wavelength division multiplexed optical signal and a natural emission light discrimination signal that appear in the electrical signal input from the photo detector 618 with reference to the control signal. Since the wavelength of the natural emission discrimination signal coincides with the reflection wavelengths of the optical fiber Bragg gratings 610 and 612, when the natural emission emission discrimination signal on the time axis and the position information of the optical signal are used, the wavelength division multiplexing is performed from the wavelength of the natural emission discrimination signal. The offset value of the band pass optical variable filter 616 for the control signal applied when the wavelength of each of the optical signals is measured may be corrected. In addition, the signal processor 620 may measure the light intensity of the wavelength division multiplexed optical signal using the sensitivity value of the photo detector 618. In addition, by measuring the light intensity of the peripheral wavelength of the wavelength division multiplexed optical signal to measure the optical signal to noise ratio of the wavelength division multiplexed optical signal.

In this method, there is no wavelength division multiplexed optical signal input to the optical fiber Bragg grating because the wavelength division multiplexed optical signal is already reflected by the signal band reflection optical filter 608. For example, even if the wavelength-division multiplexed optical signal is input to the optical fiber Bragg grating without being 100% reflected by the signal band reflective optical filter 608, the ratio reflected by the optical fiber Bragg grating is not only small but also reflected mostly by the signal band reflective optical filter 608. Therefore, interference by the wavelength division multiplexed optical signal reflected from the optical fiber Bragg grating hardly occurs.

As described above, according to the apparatus for measuring the wavelength, the light intensity, and the optical signal-to-noise ratio of an optical signal in the wavelength division multiplex optical communication according to the present invention, the following advantages are provided.

First, it does not require the use of an active optical device, which has been a conventional problem.

Second, the optical intensity and optical signal-to-noise ratio measurement error caused when the wavelength division multiplexed optical signal is reflected in the optical fiber Bragg grating in the prior art (problem of FIG. 4). The natural emission light discrimination signal can be separated and detected by different light detectors. In addition, the method of FIG. 6 may solve the problem of FIG. 4 by using a signal band reflection optical filter. Therefore, the accuracy of optical intensity and optical signal-to-noise ratio measurement can be improved.

The technical spirit of the present invention has been described above with reference to the accompanying drawings. However, the present invention has been described by way of example only, and is not intended to limit the present invention. In addition, it is obvious that any person skilled in the art may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (23)

In the apparatus for measuring the wavelength, light intensity and optical signal-to-noise ratio of an optical signal in wavelength division multiplex optical communication, Optical amplifying means for receiving and amplifying a wavelength division multiplexed optical signal and outputting natural emission light; Branching means for branching a predetermined portion of the output of the optical amplifying means; A band pass optical variable filter means for scanning the output light of the branching means while the transmission wavelength is moved in accordance with a control signal; Optical rotating means for rotating the input and the output of the optical signal in a clockwise direction; Reflecting means for reflecting only a specific wavelength component of the natural emission light and outputting a natural emission light discriminating signal; Optical / electric conversion means for converting the intensity of the received light into an electrical signal; Signal processing means for calculating the wavelength, light intensity, and optical signal-to-noise ratio of the wavelength-division multiplexed optical signal over time using the electrical signal and the control signal output from the optical / electric conversion means; An apparatus for measuring wavelength, light intensity, and optical signal-to-noise ratio of an optical signal in a wavelength division multiplex optical communication comprising the bandpass optical variable filter means and a control signal generating means for providing a control signal to the signal processing means . The apparatus of claim 1, wherein the optical amplifying means is a rare earth-added optical fiber amplifier. The wavelength, optical intensity, and optical signal-to-noise ratio of the optical signal in the wavelength division multiplex optical communication. 2. The apparatus of claim 1, wherein the optical amplifying means is a semiconductor optical amplifier. The wavelength, optical intensity, and optical signal to noise ratio of the optical signal in the wavelength division multiplex optical communication. The apparatus of claim 1, wherein the optical amplifying means is a Raman optical amplifier. 5. The apparatus of claim 1, wherein the optical amplification means is a Raman optical amplifier. The apparatus of claim 1, wherein the bandpass optical variable filter means is a Fabry-Perot variable filter. 2. The apparatus of claim 1, wherein the bandpass optical variable filter means is an integrated optical device comprising a grating. 2. The apparatus of claim 1, wherein the bandpass optical variable filter means is a multilayer thin film element. The wavelength, optical intensity, and optical signal to noise ratio of the optical signal in the wavelength division multiplex optical communication. 2. The apparatus of claim 1, wherein the bandpass optical variable filter means is an acoustic-optic filter. The apparatus of claim 1, wherein the wavelength and the light intensity and the optical signal-to-noise ratio of the optical signal are measured in a wavelength division multiplex optical communication using a 2 × 1 optical coupler instead of the optical rotating means. 2. The apparatus of claim 1, wherein the reflecting means is an optical fiber Bragg grating. The wavelength, optical intensity, and optical signal to noise ratio of the optical signal in the wavelength division multiplex optical communication. The apparatus of claim 1, wherein the reflecting means is an integrated optical device including a grating. In the apparatus for measuring the wavelength, light intensity and optical signal-to-noise ratio of an optical signal in wavelength division multiplex optical communication, Optical amplifying means for receiving and amplifying a wavelength division multiplexed optical signal and outputting natural emission light; Branching means for branching a predetermined portion of the output of the optical amplifying means; Signal band reflection optical filter means for reflecting light in a wavelength signal band in which the wavelength division multiplexed optical signal is used, and passing light in the remaining wavelength signal band; Reflecting means for reflecting only a specific wavelength component of the natural emission light and outputting a natural emission light discriminating signal; Band-pass optical variable filter means for scanning the light obtained by combining the wavelength-division multiplexed optical signal reflected by the signal band reflection optical filter means and the natural emission light discrimination signal output from the reflection means according to the control signal; Optical / electric conversion means for converting the intensity of light output from the bandpass optical variable filter means into an electric signal; Signal processing means for calculating the wavelength, light intensity, and optical signal-to-noise ratio of the wavelength-division multiplexed optical signal over time using the electrical signal and the control signal output from the optical / electric conversion means; And a control signal generating means for providing a control signal to the band pass optical variable filter means and the signal processing means. 13. The apparatus of claim 12, wherein the optical amplifying means is a rare earth-added optical fiber amplifier. 13. The apparatus of claim 12, wherein the optical amplifying means is a semiconductor optical amplifier. The wavelength, optical intensity, and optical signal to noise ratio of the optical signal in the wavelength division multiplex optical communication. The apparatus of claim 12, wherein the optical amplifying means is a Raman optical amplifier. 15. The apparatus of claim 12, wherein the optical amplification means is a Raman optical amplifier. 13. The apparatus of claim 12, wherein the bandpass optical variable filter means is a Fabry-Perot variable filter. 13. The apparatus of claim 12, wherein the bandpass optical variable filter means is an integrated optical element comprising a grating. 13. The apparatus of claim 12, wherein the bandpass optical variable filter means is a multilayer thin film element. The wavelength, optical intensity, and optical signal to noise ratio of the optical signal in the wavelength division multiplex optical communication. 13. The apparatus of claim 12, wherein the bandpass optical variable filter means is an acoustic-optic filter. The apparatus of claim 12, wherein the wavelength and the light intensity and the optical signal-to-noise ratio of the optical signal are used in the wavelength division multiplex optical communication using a 2 x 1 optical coupler as the optical rotating means. 15. The method of claim 12, wherein the wavelength division multiplexed optical signal passing through the reflecting means and the optical emission terminal further comprises an optical terminator for extinction without reflecting the missing light. Device for measuring wavelength, light intensity, and optical signal-to-noise ratio. 13. The apparatus of claim 12, wherein the reflecting means measures the wavelength of the optical signal, the light intensity, and the optical signal-to-noise ratio in the wavelength division multiplex optical communication wherein the reflection wavelength is an optical fiber Bragg grating. 13. The apparatus of claim 12, wherein the reflecting means is an integrated optical device including a grating.