JP2005310920A - WDM signal monitor module - Google Patents

Abstract

An object of the present invention is to reduce the manufacturing cost of a WDM signal monitor module while maintaining high measurement accuracy.
A WDM signal monitor module that irradiates a photodiode array 2 with spectral light from a wavelength-division-multiplexed light dispersion element 1 and monitors the wavelength-division multiplexed light by the output of the photodiode,
The photodiode array 2 includes a plurality of sets of subarrays 4 in which strip-shaped unit photodiodes 3 are arranged in parallel in the width direction at a predetermined pitch (P), and are shifted in a direction perpendicular to the arrangement direction by shifting the number of sets by one pitch. Arranged and formed
The light intensity distribution is detected by synthesizing the output of the spectral light irradiated to each subarray 4.
[Selection] Figure 1

Description

  The present invention relates to a WDM signal monitor module.

  In optical transmission systems, especially WDM (Wavelength Dividion Multiplexing) systems that are wavelength-multiplexed for the purpose of increasing transmission capacity, it is important to monitor the wavelength and optical power of each signal with high accuracy in order to understand the system operating status. As a monitor module for this purpose, one disclosed in Patent Document 1 is known.

In this conventional example, the monitor module has a diffraction grating that splits a WDM signal and a photodiode array in which strip-shaped unit photodiodes are arranged in parallel in the width direction. When wavelength-division multiplexed light is split by a diffraction grating, each channel light is collected at a different position of the photodiode array, so that the peak frequency, light intensity, etc. are known by analyzing the output from the unit photodiode. be able to.
JP 2004-56700 A

  However, in the above-described conventional example, in order to monitor channel light with sufficient resolution, it is necessary to use a photodiode array having unit photodiodes with sufficiently small width dimensions, which increases the cost. There is a problem of end.

  The present invention has been made to eliminate the above drawbacks, and an object of the present invention is to provide an inexpensive WDM signal monitor module with high measurement accuracy.

  In the present invention, the monitor light is dispersed by the dispersive element 1 such as a diffraction grating and irradiated to the photodiode array 2. The photodiode array 2 is arranged in a direction orthogonal to the parallel arrangement direction by shifting a plurality of pairs of subarrays 4 in which strip-shaped unit photodiodes 3 are arranged in parallel in the width direction at a predetermined pitch (P) by one pitch. Formed.

  As shown in FIGS. 1 (a) and 1 (b), the amount of light applied to the photodiode array 2 is taken out and synthesized for each sub-array 4 and arranged at a small pitch as shown in FIGS. 1 (c) and 1 (d). An output equivalent to that obtained by the photodiode array 2 according to the conventional example can be obtained.

  In the present invention, in which the same effect can be obtained without arranging the unit photodiodes 3 at a fine pitch, an increase in cost due to a finer pitch of the unit photodiodes 3 can be avoided. Can be achieved.

  According to the present invention, an inexpensive WDM signal monitor module with high measurement accuracy can be obtained.

  FIG. 2A shows a WDM signal monitor module. In the figure, 7 is an optical fiber for introducing WDM signal monitor light into the monitor module, 8 is a depolarizer, and 9 is a collimator lens. Reference numeral 1 denotes a diffraction grating as a dispersive element, and the monitor light converted into parallel light by the collimator lens 9 is dispersed by the wavelength by the diffraction grating 1 and guided to the photodiode array 2 via the focusing lens 10 and the mirror 11. Is done.

  An optical switch 5 is interposed between the mirror 11 and the photodiode array 2, and the optical path of the reflected light from the mirror 11 is alternately changed between subarrays 4 and 4 described later. The timing of changing the optical path coincides with a monitoring cycle of about 100 (msec) to 1 (sec).

  As shown in FIG. 1A, the photodiode array 2 includes a plurality of strip-shaped unit photodiodes 3, 3,. Several unit photodiodes 3 are arranged in the width direction to form a subarray 4, and the subarrays 4 having the same structure are arranged in the vertical direction to form the photodiode array 2.

  In this embodiment including two sets of sub-arrays 4, 4, the upper and lower sub-arrays 4 are shifted by a half (P / 2) of the pitch (P) between the unit photodiodes 3 in the juxtaposed direction. The unit photodiodes 3 are arranged so that the direction in which the monitor light is dispersed for each wavelength is aligned. As a result, the position of each unit photodiode 3 corresponds to the wavelength light that is split by the diffraction grating 1 and converges on the unit photodiode 3.

  Although FIG. 1A shows the case where the photodiode array 2 is constituted by two sets of subarrays 4, it can also be constituted by two or more sets of subarrays 4. In this case, adjacent subarrays 4 are also possible. The shift amount of the pitch (P) between the unit photodiodes 3 is set to a fraction of the number of subarrays 4. For example, when there are three sets of subarrays 4, the pitch (P) shift amount is 1 / It becomes 3 pitches.

  FIG. 1A schematically shows monitor light condensed on the upper sub-array 4 by the optical switch 5. In the drawing, a solid line circle indicates light formed by one of multiplexed optical signals. Spots and circles of adjacent chain lines respectively indicate light spots formed by optical signals multiplexed with different wavelengths.

  Now, paying attention to the light spot indicated by the solid line, the three unit photodiodes 3n-1, 3n, 3n + 1 irradiated with the light spot generate a photocurrent corresponding to the magnitude of the light energy. Occur. The output from these unit photodiodes 3 is plotted with the vertical axis in FIG. 1B, and the numbers given to the points in the figure correspond to the output values from the unit photodiodes 3 of the same number. In FIG. 1B, the horizontal axis indicates the center in the width direction of the unit photodiode 3, that is, the wavelength.

  From this state, when the optical switch 5 is operated to switch the optical path of the monitor light in the direction of the lower subarray 4, the light spot moves to the position indicated by the broken line in FIG. If the irradiation conditions such as the irradiation time and area in this state are the same as the irradiation conditions for the upper subarray 4 described above, the photocurrent indicated by points 3m and 3m + 1 in FIG. Occur.

  When the output values from the subarrays 4 obtained at different times are synthesized by a synthesis means (not shown), an approximate curve (C) is obtained, which is obtained by the conventional example as shown in FIG. It becomes similar to the obtained approximate curve (C ′), and by analyzing this, the peak wavelength, optical signal level, etc. can be known.

  In the above example, the case where the optical path of the monitor light is changed by using the optical switch 5 has been shown, but in addition to this, as shown in FIGS. It is also possible to irradiate the subarray 4 simultaneously with the monitor light under the same conditions, and select the irradiation side subarray 4 with the optical shutter 6 interposed in the optical path. Simultaneous irradiation to the sub-array 4 by the monitor light can be realized by, for example, dividing the monitor optical path by amplitude.

Further, in this case, the same operation can be performed by switching the output from the sub-array 4 at a predetermined timing without interposing the optical shutter 6.
In the above description, a case where a complete light spot of monitor light is formed on each subarray 4 has been described. However, if the irradiation conditions for the upper and lower subarrays 4 are the same, as shown in FIG. If the light spot protrudes from the subarray 4 or the photodiode array 2 is composed of two sets of subarrays 4, the center of the light spot is between the subarrays 4 as shown in FIG. The light may be condensed so as to be located at the boundary.

  In the modification shown in FIG. 3B, the output from the sub-array 4 other than the irradiation target is blocked by an appropriate switch. In the modification shown in FIG. 3C, the output of the subarray 4 is selected by a switch even if the irradiation subarray 4 is alternately changed using the optical shutter 6 or the optical shutter 6 is not used. It may be a thing.

FIG. 4A is a diagram illustrating a photodiode array according to the present invention, FIG. 4B is a diagram illustrating a composite of subarray outputs, FIG. 4C is a diagram illustrating a conventional photodiode array, and FIG. It is an output figure of a prior art example. It is a figure which shows a WDM signal monitor module, (a) is a figure which shows 1st Embodiment, (b) is a figure which shows other embodiment. It is a figure which shows the condensing state of the monitor light to a photodiode array, (a) is a figure which shows simultaneous irradiation, (b) is a figure which shows a modification, (c) is a figure which shows another modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dispersive element 2 Photodiode array 3 Unit photodiode 4 Subarray 5 Optical switch 6 Optical shutter P Pitch

Claims (4)

A WDM signal monitor module that irradiates a photodiode array with spectral light from a wavelength-division-multiplexed light dispersion element, and monitors the wavelength-division-multiplexed light by the output of the photodiode,
The photodiode array is formed by disposing a plurality of sets of subarrays in which strip-shaped unit photodiodes are arranged in parallel in the width direction at a predetermined pitch and arranging them in a direction perpendicular to the arrangement direction,
A WDM signal monitor module that detects the light intensity distribution by synthesizing the output of the spectral light emitted to each subarray. 2. The WDM signal monitor module according to claim 1, further comprising an optical switch that distributes the monitor light to any one of the sub-arrays of the photodiode array at a predetermined timing. Simultaneously irradiate each subarray with monitor light under the same conditions,
The WDM signal monitor module according to claim 1, wherein the irradiation side sub-array is switched at a predetermined timing by an optical shutter interposed in the optical path. Simultaneously irradiate each subarray with monitor light under the same conditions,
2. The WDM signal module according to claim 1, wherein the outputs from the subarrays selected by alternately connecting and disconnecting the outputs from the subarrays at a predetermined timing are used as synthesis target outputs.

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