JP4445464B2 - Optical wavelength measuring device - Google Patents

Description

  The present invention relates to a technique for easily obtaining accurate information on time versus wavelength of light to be measured whose wavelength periodically sweeps and changes.

  Various measurement systems using light sweep the wavelength of light applied to the object to be measured within a predetermined range to obtain characteristics of the object to be measured with respect to the wavelength, and are generally used in such measurement systems. As one of the variable wavelength light sources, an external resonator type has been conventionally used.

  As shown in FIG. 11, the external resonator type variable wavelength light source makes the light emitted from one end face of the semiconductor laser 1 incident on the diffraction grating 2 and the diffracted light emitted from the diffraction grating 2 is reflected by the mirror 3. The diffraction grating 2 is folded back and the diffracted light corresponding to the folded light is returned to the semiconductor laser 1. The light resonates at a wavelength determined by the optical path length from the semiconductor laser 1 via the diffraction grating 2 to the mirror 3 and the angle of the mirror 3 with respect to the diffraction grating 2, and the light P having the resonance wavelength is converted to the zeroth order of the diffraction grating 2. It can be extracted as reflected light or as emitted light from the other end face of the semiconductor laser 1.

  Here, the semiconductor laser 1, the diffraction grating 2, and the mirror 3 are arranged in a predetermined manner, and the center position of the angle change of the mirror 3 is selected, whereby the wavelength of the emitted light P is continuously changed with respect to the angle change of the mirror 3. Can be changed.

  As a mirror 3 used for a variable wavelength light source having such a structure, a so-called MEMS structure having a small size and a light weight has been realized in recent years by etching processing on a semiconductor substrate, and high-speed wavelength sweeping of several hundred Hz or more is possible. ing.

  However, variable wavelength light sources that perform high-speed wavelength sweeps as described above are susceptible to fluctuations in wavelength, particularly the wavelength sweep range, due to the effects of noise and hysteresis, so accurate wavelength information must be detected at each time. There is.

  As a technique for accurately obtaining wavelength information of light swept within a predetermined range, there is a method of using a Fabry-Perot type optical filter called an etalon having a plurality of transmission wavelength bands with one element.

  As shown in FIG. 12A, the etalon has wavelength selection characteristics in which transmission wavelength bands B0, B1,... Of center wavelengths λ0, λ1,. ing.

  Therefore, for example, when light to be measured that is swept linearly from wavelength λa to wavelength λb is incident on this etalon, and the transmitted light is incident on a light receiver, a light reception signal as shown in FIG. can get.

  The timings t1 to t6 at which the level of the received light signal reaches a peak are timings at which the wavelengths of the light to be measured coincide with the center wavelengths λ2 to λ7 of the transmission wavelength bands B2 to B7 of the etalon, respectively. From t6 and the central wavelengths λ2 to λ7, the wavelength at an arbitrary time can be obtained.

  However, if the wavelength sweep range of the light to be measured fluctuates by a width larger than the wavelength interval Δλ, the relationship between each timing at which the level of the received light signal peaks and the transmission wavelength band of the etalon is not uniquely determined. The relationship with the wavelength cannot be obtained correctly.

  As a technique for solving this, by obtaining an approximate wavelength of incident light using a slope filter whose transmittance for incident light changes monotonously with respect to the change in wavelength, the timing at which the level of transmitted light of the etalon peaks There has been proposed a method for accurately associating a transmission wavelength band with time-wavelength information of light to be measured (for example, Patent Document 1).

JP 2004-132704 A

  However, as described above, in the optical wavelength measurement device using both the slope filter and the etalon, it is necessary to obtain the level of the incident light and the level of the outgoing light of the slope filter. The one branched light is incident on the first light receiver, the other branched light is incident on the second light receiver via the slope filter, and the other branched light is incident on the third light receiver via the etalon. The structure becomes complicated and the optical system becomes complicated.

  In addition, the level value of the received light signal is greatly affected by the wavelength dependence of the optical element and the light receiver, so the accuracy of the transmittance obtained from the calculation of the level value is low, and in some cases the level of the transmitted light of the etalon In some cases, the timing at which the peak reaches cannot be correctly associated with the transmission wavelength band.

  Furthermore, since transmittance calculation processing is required, it may not be possible to cope with high-speed sweep.

  An object of the present invention is to solve this problem and to provide an optical wavelength measuring device capable of obtaining, at a high speed, accurate information on time-to-wavelength of wavelength-swept measured light with a simpler configuration. .

In order to achieve the object, an optical wavelength measuring device according to claim 1 of the present invention comprises:
Branching means (21) for receiving and branching light to be measured whose wavelength is periodically swept;
A first optical filter (22) having a plurality of transmission wavelength bands each having a center wavelength within a wavelength sweep range of the light to be measured, and receiving a first branched light branched by the branching means;
A branch wavelength having a center wavelength within a wavelength sweep range of the light to be measured, and having at least one transmission wavelength band overlapping with any one of the transmission wavelength bands of the first optical filter within the wavelength sweep range; A second optical filter (23) for receiving the second branched light branched by the means;
A light receiving unit (25) for detecting the intensity of the first transmitted light transmitted through the first optical filter and the second transmitted light transmitted through the second optical filter;
Each of the intensity of the first transmitted light reaches a peak within a period in which the wavelength of the light to be measured monotonously changes in response to an output signal of the light receiving unit and a direction signal indicating a change direction of the wavelength of the light to be measured. The timing and the timing at which the intensity of the second transmitted light becomes equal to or higher than a predetermined value or reaches a peak after exceeding the predetermined value are detected, and the first transmitted light is detected based on the timing detected for the second transmitted light. An optical wavelength measuring device comprising: a processing unit (30) that specifies a wavelength of each detected timing and obtains a time-to-wavelength relationship of the measured light;
The light receiving unit receives the first transmitted light and the second transmitted light on a common light receiving surface, and outputs a single signal corresponding to the sum of the intensities of the first transmitted light and the second transmitted light. It is composed of a light receiver (25a),
The processing unit detects a timing at which the sum signal exceeds a predetermined threshold value, and specifies a wavelength at each timing at which the intensity of the first transmitted light reaches a peak based on the timing. .

Moreover, the optical wavelength measuring device of Claim 2 of this invention is the optical wavelength measuring device of Claim 1 ,
One of the transmission wavelength bands of the second optical filter overlaps the transmission wavelength band of the longest center wavelength of the first optical filter within the wavelength sweep range of the light to be measured. Is overlapped with the shortest transmission wavelength band of the center wavelength of the first optical filter within the wavelength sweep range of the light to be measured,
Wherein the processing unit obtains the first to the sum signal the direction signal information and waveform information of the Kazunobu No. in the period until a predetermined time elapses from a timing that exceeds the threshold value after the direction signal changes And based on this acquired information, the wavelength of each timing when the intensity | strength of said 1st transmitted light becomes a peak is specified, It is characterized by the above-mentioned.

  As described above, in the optical wavelength measurement device of the present invention, the light to be measured whose wavelength changes periodically is branched, and the first branched light is divided into a plurality of transmission wavelengths each having a central wavelength within the wavelength sweep range. The first optical filter having a band is incident, the second branched light is incident on a second optical filter having a transmission wavelength band having a central wavelength within the wavelength sweep range of the light to be measured, and the first optical filter and the second light The first transmitted light and the second transmitted light that have passed through the filter are received by the light receiver of the light receiving unit, and based on the output signal of the light receiving unit and the direction signal indicating the change direction of the wavelength of the measured light Each timing at which the intensity of the first transmitted light peaks during a period in which the wavelength of the light monotonously changes, and a timing at which the intensity of the second transmitted light reaches a peak or exceeds a predetermined value. At the timing of detecting and detecting the second light transmitted light Identifying a wavelength of the timings detected for the first transmitted light Zui, seeking the order of time versus wavelength of the light to be measured.

  For this reason, the optical system can be simply configured as compared with the conventional structure using the slope filter, and the time of the light to be measured can be measured only by the information of the detected timing without performing calculation processing such as transmittance. Wavelength information can be obtained, and high-speed processing is possible.

  In addition, the absolute value of the transmittance obtained from the level value of the received light signal, which is greatly affected by the wavelength dependence of the optical element and the light receiver, is not used, but the peak wavelength of the received light power and its time are used for the calculation. Therefore, highly accurate wavelength measurement is possible.

  If one of the transmission wavelength bands of the second optical filter overlaps one of the transmission wavelength bands of the first optical filter, the combined transmission light of both optical filters or the transmission light of both optical filters By adding the received light signal, it can be detected by simple level comparison processing that the wavelength of the light under measurement has entered the overlapping transmission wavelength band.

  Further, when the light receiving unit is configured by a single light receiver that receives the first transmitted light and the second transmitted light on a common light receiving surface, the optical system can be further simplified.

  In addition, one of the transmission wavelength bands of the second optical filter overlaps the transmission wavelength band of the longest center wavelength of the first optical filter within the wavelength sweep range, and another one of the transmission wavelength bands of the second optical filter is the wavelength. In the case where it overlaps the transmission wavelength band with the shortest center wavelength of the first optical filter within the sweep range, the wavelength of the light to be measured becomes the transmission wavelength band with the longest central wavelength of the first optical filter within the wavelength sweep range. The timing of entering and the timing of entering the transmission wavelength band with the shortest center wavelength can be detected with a simple level comparison process, and the timing at which the wavelength of the light to be measured is near both ends of the sweep range can be easily identified and required for computation Information can be obtained without waste.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration of an optical wavelength measuring device 20 to which the present invention is applied.

  As shown in FIG. 1, this optical wavelength measuring device 20 splits measured light P, which is emitted from a variable wavelength light source (not shown) and whose wavelength changes at a constant cycle, from a half mirror 21a and a mirror 21b. 21 is branched into two optical paths, one of the first branched lights Pa is incident on the first optical filter 22 and the other second branched light Pb is incident on the second optical filter 23.

  The signal Q input together with the measured light P is a direction signal indicating the direction of change of the wavelength of the measured light P. For example, 1 (high level) during a period in which the wavelength becomes shorter as time elapses, It is assumed that 0 (low level) is input during a period in which the wavelength increases with time.

  The first optical filter 22 is a Fabry-Perot optical filter called an etalon, and has a high transmission as shown in FIG. 2A within a desired wavelength variable range (for example, 1500 to 1600 nm) of the light P to be measured. It has a plurality of transmission wavelength bands B0 to B9 (10 in this example) indicating the rate. The center wavelengths of the transmission wavelength bands B0 to B9 are λ0 to λ9, and the interval Δλ can be regarded as constant.

  Note that the transmission wavelength band of the first optical filter 22 exists outside the desired wavelength variable range of the light to be measured P, and the wavelength sweep range of the light to be measured P varies so that the transmission wavelength band other than B0 to B9 is obtained. However, the transmission wavelength bands B0 and B9 in the vicinity of both ends of the desired wavelength sweep range are set on the inner side in consideration of the fluctuation of the wavelength sweep range of the light P to be measured. Even if the wavelength sweep range fluctuates, the transmission wavelength bands B0 and B9 are always transmitted within the period.

  The second optical filter 23 is a Fabry-Perot type optical filter called an etalon like the first optical filter 22, and is centered within the wavelength variable range of the measured light P as shown in FIG. It has two transmission wavelength bands C0 and C1 having a wavelength and high transmittance. The transmission wavelength bands C0 and C1 overlap with the transmission wavelength bands B0 and B9 at both ends of the first optical filter 22, and the center wavelengths of the transmission wavelength bands C0 and C1 coincide with λ0 and λ9 (strictly speaking, There is an error, but the effect of that error will be described later).

  The first transmitted light Pa ′ transmitted through the first optical filter 22 and the second transmitted light Pb ′ transmitted through the second optical filter 23 are incident on the light receiving unit 25.

  The light receiving unit 25 is for detecting the intensities of the first transmitted light Pa ′ and the second transmitted light Pb ′. Here, the transmitted light Pa ′ and Pb ′ are received by a common light receiving surface, and both transmitted light is transmitted. It is composed of a single light receiver 25a that outputs a signal V whose level changes in accordance with the sum of the intensities of the light Pa 'and Pb' (hereinafter referred to as sum signal). In order to prevent interference, the transmitted light Pa ′ and Pb ′ are incident on different positions on the light receiving surface of the light receiver 25a.

  The sum signal V is input to the processing unit 30 together with the direction signal Q. In the processing unit 30, the timing at which the intensity of the first transmitted light Pa ′ peaks and the intensity of the second transmitted light Pb ′ become equal to or greater than a predetermined value within a period in which the wavelength of the measured light P changes monotonously. Alternatively, the timing of the peak is detected, the wavelength of each timing detected for the first transmitted light Pa ′ is specified from the timing detected for the second light transmitted light Pb ′, and the time-wavelength relationship of the measured light P Ask for.

  However, in this example, the transmission wavelength bands B0 and B9 and the transmission wavelength bands C0 and C1 overlap, and the center wavelengths thereof also coincide with each other at λ0 and λ9. The timing that coincides with the center wavelengths λ0 and λ9 of the transmission wavelength bands B0 and B9 of the optical filter 22 and the timing that coincides with the center wavelengths of the transmission wavelength bands C0 and C1 of the second optical filter 23 are the same. The processing unit 30 specifies the wavelength of the timing at which the intensity of the first transmitted light Pa ′ reaches a peak by using the configuration of the light receiving unit 25 and the overlapping of the transmission wavelength bands of the two optical filters 22 and 23. The relationship between the time of measurement and the wavelength of the light P to be measured is obtained.

  That is, as shown in FIG. 1, the sum signal V output from the light receiving unit 25 is input to the controller 31 and the A / D converter 32.

  The controller 31 compares the sum signal V with a preset threshold value Vr, and the timing at which the signal V first exceeds the threshold value Vr after the direction signal Q is switched from 0 to 1 or 1 to 0 is set as data. The acquisition start timing ts and then the timing when the signal V exceeds the threshold value Vr is set as the data acquisition end timing te, and the sum signal V is sampled by the A / D converter 32 only during the period ts to te, It is converted into digital waveform information Dv and stored in the first memory 33 together with the direction signal Q information.

  The computing unit 34 obtains a time-wavelength relationship from the waveform information Dv and the direction signal Q stored in the first memory 33, and stores the information in the second memory 35.

  Here, the calculation unit 34 determines a function (for example, a cubic function) λ = F (t) that approximately represents the relationship between time and wavelength during a period in which the wavelength of the light P to be measured is monotonically changing. When the coefficient is obtained based on the waveform information Dv and the direction signal Q, stored in the second memory 35 together with time information (for example, ts, te) during that period, and output of the wavelength at the time tx designated from the outside is requested Based on the information stored in the second memory 35, the wavelength λx of the request time is calculated.

Next, the operation of the optical wavelength measuring device 20 will be described.
For example, as shown in FIG. 3A, the wavelength of the incident measurement light P is swept within a range from a wavelength longer than the wavelength λ0 to a wavelength shorter than the wavelength λ9 at a constant period. Here, a period in which the wavelength of the light P to be measured is monotonously changed toward a shorter wavelength will be described, but the same processing is performed for a period in which the wavelength is monotonously changed toward a longer wavelength.

  At this time, the first branched light Pa and the second branched light Pb branched by the branching unit 21 are incident on the first optical filter 22 and the second optical filter 23, respectively, and the intensity changes as shown in FIG. The first transmitted light Pa ′ and the second transmitted light Pb ′ whose intensity changes as shown in FIG. 3C are incident on the light receiver 25 a of the light receiving unit 25.

  Here, the incident intensity of the first transmitted light Pa ′ with respect to the light receiver 25a peaks at timings t0 to t9 when the wavelength of the light P to be measured coincides with the center wavelengths λ0 to λ9 of the transmitted wavelength bands B0 to B9, respectively. Further, the incident intensity of the second transmitted light Pb ′ peaks at timings t0 and t9.

  Therefore, as shown in FIG. 4A, the sum signal V has peak values Vp0 and Vp9 at timings t0 and t9 when the wavelength of the measured light P becomes λ0 and λ9, and the wavelength of the measured light P is from λ1 to λ1. At each timing t1 to t8 when λ8 is reached, the peak values Vp1 to Vp8 are smaller than the peak values Vp0 and Vp9.

  This sum signal V is input to the controller 31 together with a direction signal Q (Q = 1 in this case) shown in FIG. The controller 31 compares the large peak values Vp0 and Vp9 with the threshold value Vr set between the small peak values Vp1 to Vp8 and the sum signal V, and after the direction signal Q switches from 0 to 1. First, a timing ts when the sum signal V exceeds the threshold value Vr and a timing te when the sum signal V exceeds the threshold value Vr second are detected, and the A / D conversion process by the A / D converter 32 is performed only during that time. For example, a control signal for controlling the storage process of data by the first memory 33 is output as shown in FIG.

  For this reason, the time series data (waveform information Dv) of the sum signal V and the value of the direction signal Q from time ts to te are stored in the first memory 33.

  When the waveform information Dv and the direction signal Q are stored in the first memory 33, if the write address of the first memory 33 is returned to the initial value at each data acquisition start timing, a memory with a small capacity can be used. .

  The calculation unit 34 reads out the waveform information Dv and the direction signal Q, and obtains the respective timings t1 to t8 at which the magnitude is in a range smaller than the threshold value Vr as the timing at which the first transmitted light Pa ′ reaches a peak. Since the value of the direction signal Q at this time is 1 indicating the wavelength decreasing direction period, the wavelengths are associated with the timings t1 to t8 in the order of λ1 to λ8. When the value of the direction signal Q is 0, the wavelengths are associated with the timings t1 to t8 in the order of λ8 to λ1.

  Then, an approximate function is obtained by the least square method using the combinations (ti, λi) of the timings t1 to t8 and the corresponding wavelengths λ1 to λ8, and coefficient information of the approximate function together with information of the periods ts to te is obtained. 2 Store in the memory 35.

  Thereafter, the above process is repeated, and information indicating the relationship between time and wavelength for each period in which the wavelength of the light P to be measured monotonously changes is obtained and stored in the second memory 35 sequentially.

  For example, when the time information tx is designated from the outside, the information of the function F (t) of the period including the time is read from the second memory 35, the designated time tx is substituted, and the wavelength λx at the time is designated. = F (tx) is calculated and notified to the outside.

  The above processing may be performed for a period in which the wavelength of the light P to be measured monotonously decreases and a period in which the wavelength of the measured light P monotonously increases, or may be performed only for one monotonous change period.

  Further, as in this embodiment, when the output signal of the light receiving unit 25 is a sum signal corresponding to the sum of the intensities of the first transmitted light Pa ′ and the second transmitted light Pb ′, the first optical filter 22 and the second optical filter 22 If there is a difference in the center wavelength between overlapping transmission wavelength bands of the optical filter 23, the sum signal V may peak when the wavelength of the light P to be measured is between the two center wavelengths. An error occurs when the calculation is performed with the peak timing associated with the center wavelength of the transmission wavelength band of the first optical filter 22.

  Therefore, in this embodiment, the combination of the peak timing and the wavelength for the overlapping transmission wavelength band is excluded from the calculation.

  Thus, in the optical wavelength measuring device 20 of the embodiment, in addition to the Fabry-Perot type first optical filter 22 having a plurality of transmission wavelength bands B0 to B9 within the wavelength sweep range of the measured light P, the measured light P The second optical filter 23 having two transmission wavelength bands C0 and C1 that overlap the transmission wavelength band of the first optical filter 22 within the wavelength sweep range is used, and the second optical filter 23 is within a period in which the wavelength of the light P to be measured changes monotonously. The timing at which the intensity of the second transmitted light Pb ′ that has passed through the optical filter 23 becomes equal to or greater than a predetermined value is detected, and the timing at which the intensity of the first transmitted light Pa ′ reaches a peak is associated with the wavelength based on that timing. Therefore, even if the wavelength sweep range of the light P to be measured varies, the time-wavelength relationship can be accurately obtained.

  In addition, the optical system for calculating the light transmittance and calculation processing are not required, the structure can be simplified, and the time-to-wavelength information of the light to be measured can be obtained from only the detected timing information. High-precision processing is possible.

  Further, as in the above embodiment, the transmission wavelength band of the second optical filter 23 is overlapped with the transmission wavelength band of the first optical filter 22, and the first transmission light Pa ′ and the second transmission light Pb ′ are simply combined. When it is configured to output a sum signal V corresponding to the sum of the intensities of both transmitted lights by entering the light receiving surface of one light receiver 25a, the wavelength of the light P to be measured has entered an overlapping transmission wavelength band. Can be easily performed only by comparing the level of the sum signal V output from the light receiving unit 25, and the configuration of the light receiving unit 25 and the processing unit 30 can be simplified.

  In the above embodiment, the two transmission wavelength bands C0 and C1 of the second optical filter 23 are overlapped with the transmission wavelength band B0 having the longest central wavelength and the transmission wavelength band B9 having the shortest central wavelength, respectively. Therefore, the timing at which the sum signal V first exceeds the threshold value Vr during the period in which the wavelength of the measured light P is monotonously changed is used as the data acquisition start timing, and then the timing at which the sum signal V exceeds the threshold value Vr is the data The acquisition end timing can be set, and even if the sweep wavelength range of the light P to be measured fluctuates, waveform data within the transmission wavelength band B0 to B9 can always be acquired, and unnecessary data acquisition is not performed. Just do it.

  The data acquisition end timing may be set after a certain time has elapsed from the data acquisition start timing. Further, when data is acquired only in one of the monotonic change periods of the wavelength, the second light The transmission wavelength band of the filter 23 is made one, and this may be overlapped with one of the transmission wavelength bands B0 and B9 of the first optical filter 22.

  In the above-described embodiment, the level of the sum signal V of the light receiving unit 25 is compared to detect that the wavelength of the light P to be measured has entered the overlapping transmission wavelength band. Without specifically limiting the acquisition period, the waveform information of the sum signal V and the direction signal Q are continuously stored from a certain time (for example, when the power is turned on) as long as the storage capacity of the first memory 33 permits, and the write address is After reaching the final value, a method of returning the write address to the initial value and continuing the storage process may be adopted. In this case, the controller 31 is not required as in the processing unit 30 shown in FIG. . Further, in this case, the calculation unit 34 reaches the transmission wavelength band B0 (or B9) at the timing when the level of the sum signal V first exceeds the threshold value Vr after the direction signal Q changes. The center wavelength of each transmission wavelength band of the first optical filter 22 is specified in order for each timing of each peak lower than the threshold value Vr following this, and the above calculation is performed, Information indicating the wavelength relationship is sequentially obtained and stored in the second memory 35.

  Further, when the data acquisition period is not limited as described above, the overlapping number of the transmission wavelength band of the first optical filter 22 and the transmission wavelength band of the second optical filter may be 1, and the overlapping position is arbitrary. For example, the transmission wavelength band C0 of the second optical filter 23 may be overlapped as shown in FIG. 6B with respect to one transmission wavelength band B4 of the first optical filter 22 shown in FIG. Is possible. In addition, the overlap of the transmission wavelength bands of the first optical filter 22 and the second optical filter 23 is within a range in which it is possible to specify which of the overlapping transmission wavelength bands the wavelength of the measured light P is in. 3 or more.

  Further, in the above embodiment, the transmitted light Pa ′ of the first optical filter 22 and the transmitted light Pb ′ of the second optical filter 23 are incident on the light receiving surface of the single light receiver 25a, and both transmitted from the light receiver 25a. Although the sum signal V corresponding to the sum of the light intensities is output, like the optical wavelength measuring device 40 shown in FIG. 7, the light receiving unit 25 is connected to the first light receiver 25b that receives the first transmitted light Pa ′. And a second light receiver 25c that receives the second transmitted light Pb '. The output signals Va and Vb are added by the adder 36 of the processing unit 30 and the sum signal Vs corresponding to the sum of the intensities of both transmitted lights. Can be input to the A / D converter 32 and the controller 31, and the same processing as the sum signal V can be performed on the sum signal Vs.

  In the above embodiment, the transmission wavelength bands of the first optical filter 22 and the second optical filter 23 are overlapped. However, the transmission wavelength bands of both optical filters may be separated. However, as described above, when the data acquisition period is determined by the transmitted light of the second optical filter 23, the transmission wavelength band B0 to B9 of the first optical filter 22 shown in FIG. The transmission wavelength bands C0 and C1 of the two optical filters 23 are set in the vicinity of the transmission wavelength bands B0 and B9 at both ends (in this case, slightly inside) as shown in FIG. 8B.

  When the optical filters 22 and 23 having the wavelength selection characteristics shown in FIG. 8 are used, the first transmitted light Pa ′ and the second transmitted light Pb are used as the light receiving unit 25 as in the optical wavelength measuring device 50 shown in FIG. 'Is received by two light receivers 25b and 25c, the output signal Va of the light receiver 25b is input to the A / D converter 32 of the processing unit 30, and the output signal Vb of the light receiver 25c is input to the controller 31. To do.

  Then, the controller 31 compares the output signal Vb with a threshold value Vr ′ set to a value lower than the peak value appearing in the output signal Vb, and the output signal Vb is first set to the threshold value Vr in the monotonic change period of the wavelength. The timing at which 'is exceeded is the data acquisition start timing for the output signal Va, and the timing at which the output signal Vb exceeds the threshold value Vr' (or after a certain time has elapsed) is the data acquisition end timing for the output signal Va.

  In the case where the optical filters 22 and 23 having the wavelength selection characteristics shown in FIG. 8 are used and the data acquisition period is not limited as described above, the light receiver 25b, The output signals Va and Vb of 25c are converted into digital waveform information Dva and Dvb by A / D converters 32A and 32B, and are sequentially stored in the first memory 33 together with the direction signal Q, and are stored in the first memory 33 by the arithmetic unit 34. The timing at which the stored output signal Vb exceeds the threshold value Vr ′ is detected as the timing at which the wavelength of the measured light P enters the transmission wavelength band of the second optical filter 23, and the timing and the value of the direction signal Q From this, the wavelength at each timing when the output signal Va peaks is specified, and information indicating the relationship between time and wavelength is obtained in the same manner as described above.

  As described above, when the transmission wavelength bands of the two optical filters are separated from each other, the intensity of the second transmitted light Pb ′ reaches the peak, that is, the timing at which the output signal Vb reaches the peak and the second light. Since the center wavelength of the transmission wavelength band of the filter 23 can be correlated, the timing at which the output signal Vb reaches its peak is detected without performing the comparison using the threshold value Vr ′, and based on the detection timing. The wavelength of the timing at which the intensity of the first transmitted light Pa ′ reaches a peak may be specified. In this case, the timing and the wavelength at which the output signal Vb peaks can be used for calculation. .

  In addition, in the case of the configuration for obtaining information indicating the relationship between time and wavelength without limiting the data acquisition period as described above, the transmission wavelength band of the second optical filter 23 may be one, and the wavelength sweep of the light P to be measured P Even if there is a variation in the range, the number may be any number of three or more within the range in which the wavelength can be specified.

  In the above-described embodiment, the processing unit 30 is configured to calculate and output the wavelength information λx corresponding to the time tx designated from the outside. May be output spontaneously together with information on the time zone to which the information is applied, and the wavelength may be calculated on the receiving side.

The figure which shows the structure of embodiment of this invention Wavelength selection characteristic diagram of the main part of the embodiment Operation explanatory diagram of the embodiment Operation explanatory diagram of the embodiment The figure which shows the modification of the principal part of embodiment. Another wavelength selective characteristic diagram of the main part of the embodiment Configuration diagram of another embodiment of the present invention Another wavelength selective characteristic diagram of the main part of the embodiment The block diagram of another embodiment using the optical filter which has the selection characteristic of FIG. The figure which shows the modification of the principal part of embodiment of FIG. Diagram showing the configuration of an external resonant variable wavelength light source Wavelength selective characteristic diagram of etalon and diagram showing intensity change of transmitted light with respect to wavelength swept light

Explanation of symbols

  20, 40, 50: Optical wavelength measuring device, 21: Branch means, 22: First optical filter, 23: Second optical filter, 25: Light receiving unit, 25a to 25c: Light receiver, 30 ... ... Processing unit, 31 ... Controller, 32, 32A, 32B ... A / D converter, 33 ... First memory, 34 ... Calculation unit, 35 ... Second memory

Claims (2)

Branching means (21) for receiving and branching light to be measured whose wavelength is periodically swept;
A first optical filter (22) having a plurality of transmission wavelength bands each having a center wavelength within a wavelength sweep range of the light to be measured, and receiving a first branched light branched by the branching means;
A branch wavelength having a center wavelength within a wavelength sweep range of the light to be measured, and having at least one transmission wavelength band overlapping with any one of the transmission wavelength bands of the first optical filter within the wavelength sweep range; A second optical filter (23) for receiving the second branched light branched by the means;
A light receiving unit (25) for detecting the intensity of the first transmitted light transmitted through the first optical filter and the second transmitted light transmitted through the second optical filter;
Each of the intensity of the first transmitted light reaches a peak within a period in which the wavelength of the light to be measured monotonously changes in response to an output signal of the light receiving unit and a direction signal indicating a change direction of the wavelength of the light to be measured. The timing and the timing at which the intensity of the second transmitted light becomes equal to or higher than a predetermined value or reaches a peak after exceeding the predetermined value are detected, and the first transmitted light is detected based on the timing detected for the second transmitted light. An optical wavelength measuring device comprising: a processing unit (30) that identifies a wavelength of each detected timing and obtains a time-to-wavelength relationship of the measured light ;
The light receiving unit receives the first transmitted light and the second transmitted light on a common light receiving surface, and outputs a single signal corresponding to the sum of the intensities of the first transmitted light and the second transmitted light. It is composed of a light receiver (25a),
The processing unit detects a timing at which the sum signal exceeds a predetermined threshold value, and identifies a wavelength at each timing at which the intensity of the first transmitted light peaks based on the timing. Optical wavelength measuring device . One of the transmission wavelength bands of the second optical filter overlaps the transmission wavelength band of the longest center wavelength of the first optical filter within the wavelength sweep range of the light to be measured. Is overlapped with the shortest transmission wavelength band of the center wavelength of the first optical filter within the wavelength sweep range of the light to be measured,
The processing unit acquires waveform information and the direction signal information of the sum signal in a period from when the sum signal first exceeds the threshold after the change of the direction signal until a predetermined time elapses. The optical wavelength measuring device according to claim 1 , wherein a wavelength at each timing at which the intensity of the first transmitted light reaches a peak is specified based on the acquired information .

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