JP5218243B2 - Optical module - Google Patents

Description

  The present invention relates to an optical module provided with a light dispersion filter for giving desired dispersion characteristics to incident light.

  In an optical communication system that transmits an optical signal using an optical fiber, it is known that the optical signal is dispersed in the optical fiber, thereby disturbing the signal waveform and limiting the transmission distance. Dispersion is a phenomenon in which a difference in signal arrival time occurs due to a difference in refractive index for each wavelength in an optical fiber. Since an optical signal usually has a predetermined spectral width, if the transmission distance is long, the signal waveform spreads on the time axis due to dispersion, and correct information cannot be received on the receiving side.

  In a backbone network, an access network, or the like, a 1.55 μm band light source that generally minimizes loss in an optical fiber is used. The dispersion value received by the optical signal in this wavelength band within the optical fiber is about 17 ps / nm / km. Therefore, if the dispersion characteristic of the optical fiber is shifted so that the dispersion value is minimized with respect to the optical signal in the 1.55 μm wavelength band, the influence of dispersion during optical transmission can be reduced. An optical fiber in which this dispersion characteristic is shifted from a predetermined wavelength band is referred to as a dispersion shift fiber (DSF).

  However, the dispersion-shifted fiber has a more complicated refractive index distribution in the cross-sectional direction than a normal optical fiber, so the distortion of the core caused by routing during installation of the optical fiber directly affects the dispersion characteristics and disperses in the length direction. The value fluctuates. In addition, the variation of the dispersion value due to the change of the ambient temperature is large. For this reason, in a conventional optical communication system using a dispersion shifted fiber, detailed dispersion design is performed in the entire transmission line, and the cost increase of the dispersion shifted fiber manufactured based on the design result increases the distance of the transmission line. It was an obstacle to large capacity.

  Generally, in an optical fiber, the square of the transmission speed of an optical signal and the product of the dispersion value are constant. Therefore, if the optical signal has a spectral width, the transmission distance becomes shorter in inverse proportion to the square of the speed.

  For example, when a direct modulation type semiconductor laser is used as the light source, the influence of dispersion increases because the wavelength variation of the light source is large. On the other hand, when an external modulation type semiconductor laser is used as the light source, wavelength fluctuation can be suppressed by adjusting an external modulator composed of a Mach-Zehnder type, so that a transmission rate of 10 to 40 Gb / s can be realized. The effect cannot be removed.

  Therefore, in a conventional optical communication system, a dispersion compensator that provides dispersion opposite to that received by an optical signal in an optical fiber is provided on the light source side or light receiving side, thereby reducing the influence of dispersion and extending the transmission distance. The technique to do is generally adopted.

  As an example of providing such a dispersion compensator, Patent Document 1 discloses a configuration in which a dispersion compensator is provided on a transmission unit (light source side). Further, as a specific configuration of the dispersion compensator, Patent Document 2 and Patent Document 3 describe fiber ring resonator type dispersion compensators. Furthermore, a fiber grating resonator type dispersion compensator described in Patent Document 4, a multiple reflection delay plate type dispersion compensator described in Patent Document 5, and the like are also known.

  Since these dispersion compensators employ a large-scale configuration to compensate for dispersion, there is a problem that the cost of the optical communication system increases. However, since these dispersion compensators can compensate a large amount of dispersion (for example, 3000 ps / nm), they are suitable for use in an optical communication system for long-distance transmission.

  On the other hand, as an attempt to downsize the dispersion compensator, for example, Patent Document 6 describes a dispersion compensator using an etalon resonator (hereinafter referred to as an etalon-type dispersion compensator). Hereinafter, this etalon type dispersion compensator will be briefly described.

  The etalon resonator has a configuration in which two partial transmission mirrors (partial reflection layers) are arranged at a predetermined interval so as to form a reflection type resonator, and has a predetermined light transmission characteristic called FSR (free spectral range). A peak occurs at every frequency interval. FSR is a frequency determined by the arrangement interval of the partial transmission mirrors. For example, in a configuration in which a light transmission layer having a refractive index of 1.5, such as glass, is sandwiched between partial transmission mirrors, about 100 GHz at an interval of 1 mm. It becomes.

  The light incident on the etalon resonator is transmitted while being repeatedly reflected at both end faces of the partial transmission mirror. At this time, wavelength light with a large amount of transmissive component and light with a small wavelength are observed, but considering that the ratio of reflection at the end face is the same for any wavelength light, the wavelength light with a large amount of transmissive component reciprocates more. It is thought that it is transmitted with delay. Therefore, the fact that the transmission characteristics depend on the wavelength means that the delay amount varies depending on the wavelength. The etalon resonator can be used as an optical dispersion filter having a large dispersion characteristic because this delay amount greatly varies depending on the wavelength. If dispersion is given to the optical signal that is input to the optical fiber or the optical signal that is output from the optical fiber by utilizing the reverse of the dispersion characteristic of the optical fiber, the influence of the dispersion received from the optical fiber can be reduced. Can be reduced.

  In addition, a reflection type configuration that totally reflects light at one end face is also known for the etalon type dispersion compensator. When one end face is totally reflected, the light that should originally pass through the end face again passes through the etalon and returns to the incident side, so that the incident light is emitted from the same plane as the incident side without loss. At this time, the amount of dispersion received by the emitted light is the sum of the amount of light originally reflected and the amount of light originally transmitted through the end face.

  Since the etalon type dispersion compensator has almost the same transmission characteristics obtained at every predetermined frequency interval (FSR), dispersion that simultaneously compensates for multi-channel optical signals as in an optical wavelength division multiplexing (WDM) system. It can be used as a compensator.

  However, the conventional etalon type dispersion compensator can only achieve a dispersion compensation amount of about 20 ps / nm. Since the transmittance of the light dispersion filter is smaller than 100%, the optical power loss becomes large.

  On the other hand, Patent Document 7 describes an attempt to increase the amount of dispersion compensation and increase the bandwidth using a plurality of resonator-type filters. Patent Document 7 describes that dispersion characteristics can be improved by stacking three layers of resonator filters made of a dielectric multilayer film having predetermined dispersion characteristics.

  However, the configuration described in Patent Document 7 employs a reflective configuration in which the light incident surface and the light exit surface are the same in order to extract 100% of the optical power while compensating for the dispersion. Alternatively, an element (circulator) for changing the optical path of the emitted light is required, and the device configuration on the light source side or the reception side having the dispersion compensator becomes large, which is not suitable for miniaturization. Further, since the configuration compensates only for dispersion within a predetermined band, it is not suitable for multi-channel use unlike the etalon type dispersion compensator described in Patent Document 6.

  Therefore, Non-Patent Document 1 describes an example in which the configuration described in Patent Document 7 is used for multichannel applications. However, since the configuration described in Non-Patent Document 1 is a reflection type in which the light incident surface and the light emission surface are the same as in Patent Document 7, a circulator or the like is required and is not suitable for miniaturization. Furthermore, since there is a mechanism for varying the amount of dispersion, the number of parts increases and the configuration becomes complicated. In addition, although the structural example which does not use a circulator by the structure similar to the nonpatent literature 1 is described in patent document 8, it has the same problem as the nonpatent literature 1, and the optical communication system including an optical system Scale increases.

Japanese Patent Laid-Open No. 10-242910 JP-A-5-181028 JP-A-5-323391 JP 2000-252920 A Special table 2000-511655 gazette JP-A-6-160604 JP 2000-105313 A US Patent Application Publication No. 20010021053

Moss, Optical Fiber Conference, Proceedings of 2002 Annual Meeting, TuT2, page 133, Fig. 1

  The first problem is that the system configuration becomes large in an optical communication system in which a conventional dispersion compensator is provided on the light source side or the reception side.

  The reason for this is that dispersion compensation is to create a delay circuit corresponding to the wavelength component, and in order to realize a large amount of dispersion compensation, it is necessary to sufficiently lengthen the optical path for delaying the optical signal. It is.

  The second problem is that the conventional dispersion compensator loses optical power wastefully.

  The reason is that an optical signal is taken out from the optical fiber, dispersion compensation is performed, and the optical signal is returned to the optical fiber again, so that an optical coupling loss occurs.

  A third problem is that the dispersion compensation amount is small in the conventional etalon type light dispersion filter.

  This is because the conventional etalon type dispersion compensator cannot increase the dispersion compensation amount because the path for delaying light is short.

  The fourth problem is that in an optical communication system including a reflection type dispersion compensator, the optical system becomes complicated and the system scale becomes large.

  The reason is that since the reflection type dispersion compensator has the same light incident surface and light exit surface, a component for switching the light path is required.

  The present invention has been made in order to solve the problems of the conventional techniques as described above, and realizes a long transmission line while realizing miniaturization, low power consumption, and low cost. An object of the present invention is to provide an optical module including an optical dispersion filter serving as a dispersion compensator.

  Another object of the present invention is to provide an optical module including an optical dispersion filter that can be applied in a wide range by related techniques such as an optical dispersion measuring instrument, not limited to optical communication.

In order to achieve the above object, an optical module of the present invention comprises an optical fiber that is a transmission medium for an optical signal,
A reflection type light dispersion filter comprising a plurality of light transmission layers through which light is transmitted in order to compensate for dispersion received by the optical fiber, and partial reflection layers alternately arranged with the light transmission layers;
An optical active element disposed at a position avoiding an optical axis connecting the optical fiber and the light dispersion filter ;
A half mirror located on the optical axis connecting the optical fiber and the light dispersion filter, and arranged so that the optical active element is located on the optical axis of the reflected light;
Have

According to the present invention, a reflection type light dispersion filter comprising a plurality of light transmission layers through which light is transmitted in order to compensate dispersion received by an optical fiber, and partial reflection layers alternately arranged with the light transmission layers, An optical active element disposed at a position avoiding the optical axis connecting the fiber and the optical dispersion filter, and an optical active element positioned on the optical axis connecting the optical fiber and the optical dispersion filter and on the optical axis of the reflected light By adopting a configuration having a half mirror arranged so that is positioned, it is possible to give a desired dispersion characteristic to the optical signal on the optical signal transmission side or the reception side using an optical dispersion filter. The transmission distance of the optical communication system using the optical fiber can be increased without providing a large-scale dispersion compensator outside the optical module. Therefore, it is possible to reduce the size and cost of the optical communication system.

  In addition, since an optical dispersion filter that serves as an optical dispersion compensator can be built into the optical module on the optical signal transmission side or reception side, optical coupling loss is minimized, and optical power is wasted like conventional dispersion compensators. No loss.

  Further, in the light dispersion filter of the present invention, the same transmission characteristics are repeated at a predetermined frequency interval (FSR) depending on the thickness of the light transmission layer (resonator length). Therefore, if the FSR is set equal to the communication channel interval, Dispersion compensation can be performed simultaneously on a plurality of optical signals having the same communication channel interval as in the WDM communication system.

  In particular, an optical module having a reflection type light dispersion filter can arrange an optical active element at a position avoiding the optical axis connecting the optical fiber and the light dispersion filter, so that a circulator or the like is not required, and the configuration of the optical system is reduced. The simplification prevents an increase in the scale of the optical communication system.

It is sectional drawing which shows the structure of 1st Example of the light dispersion filter of this invention. FIGS. 2A and 2B are diagrams illustrating a configuration example of the multilayer film illustrated in FIG. 1, in which FIG. 1A is a cross-sectional view illustrating a configuration using a single-layer thin film, and FIG. FIG. 4C is a cross-sectional view showing a configuration using an eight-layer thin film, and FIG. 4D is a cross-sectional view showing a configuration using a 12-layer thin film. 2 is a graph showing a dispersion amount and an operation band with respect to the number of etalon resonator layers of the light dispersion filter shown in FIG. 1. 3 is a graph showing group delay characteristics of the light dispersion filter shown in FIG. 1. It is sectional drawing which shows the structure of 2nd Example of the light dispersion filter of this invention. It is sectional drawing which shows the structure of 3rd Example of the light dispersion filter of this invention. It is sectional drawing which shows the structure of 4th Example of the light dispersion filter of this invention. It is sectional drawing which shows the structure of 5th Example of the light dispersion filter of this invention. It is sectional drawing which shows the structure of 6th Example of the light dispersion filter of this invention. It is sectional drawing which shows one structural example of the optical module using the transmission type light dispersion filter of this invention. It is sectional drawing which shows one structural example of the optical module using the reflection type light dispersion filter of this invention. It is sectional drawing which shows the other structural example of the optical module using the reflection type light dispersion filter of this invention. It is sectional drawing which shows the 1st modification of the optical module using the light dispersion filter of this invention. It is sectional drawing which shows the 2nd modification of the optical module using the light dispersion filter of this invention. It is a block diagram which shows one structural example of the light dispersion measuring device using the light dispersion filter of this invention. It is a wave form diagram which shows the effect of the channel extraction method using the light dispersion filter of this invention.

  Next, the present invention will be described with reference to the drawings.

  First, an optical dispersion filter used in the dispersion compensator and the optical module of the present invention will be described.

  The etalon resonator described above becomes a light dispersion filter having the same transmission characteristics at every FSR interval. In the etalon resonator, the incident light is transmitted after reciprocating many times between the partially reflecting layers, so that an effective optical path is lengthened although it is small, and the transmission time difference (dispersion) depending on the wavelength can be increased. Dispersion can be compensated by using one etalon resonator as in the conventional dispersion compensator, but according to the calculation of the present inventor, the dispersion compensation amount is 20 ps / max at the maximum in the operating band of 20 GHz within FSR = 100 GHz. Only very small nanometers can be obtained.

  In the present invention, an effective optical path of incident light is further lengthened by bonding a plurality of etalon resonators to form a light dispersion filter. Thereby, the dispersion compensation value can be further increased. However, a simple dispersion characteristic in a wide band cannot be obtained by simply attaching an etalon resonator. This is because there is a close relationship between the dispersion characteristic with respect to wavelength and the reflectance between each etalon resonator.

  In the present invention, when the reflectance at each interface between a plurality of etalon resonators is changed and a transmission type light dispersion filter is configured, the reflectance at the interface near the center in the thickness direction is set to be the highest. In addition, the reflectance of each boundary surface is set to gradually decrease toward both end surfaces. Further, in the case of configuring a reflection type light dispersion filter, the reflectance of the incident surface is set to the lowest, the reflectance of the final end surface opposite to the incident surface is set to 100%, and each toward the final end surface, It is set so that the reflectivity of the boundary surface gradually increases. By setting the reflectivity of each boundary surface in this way, desired dispersion characteristics can be obtained over the plurality of etalon resonators as a whole.

  By the way, when designing a light dispersion filter, it is common to design the extreme value of the light dispersion filter to a desired value. For example, as described in Lenz, "Dispersive Properties of Optical Filters for WDM Systems", IEEE Journal of Quantum Electronics, 1998, No. 34, vol. 8, pp. 1390-1402, an etalon resonator is Since it has one pole, the multilayered etalon resonator as in the present invention has a transmission characteristic in which the poles of the etalon resonators overlap each other.

  In the light dispersion filter of the present invention, the value obtained by wavelength differentiation with respect to the group delay time obtained from the superposition of poles determined by each etalon resonator is the dispersion amount. In addition, in order to obtain a constant dispersion characteristic within the operating band (usually within the band corresponding to the half cycle of the FSR), the group delay characteristic is determined to be linear within the band corresponding to the half period of the FSR. A general design method for this is shown, for example, in FIG. 5 of Japanese Patent Application Laid-Open No. 2002-122732. According to the publication, when the number of poles is 3 or more, a linear group delay characteristic is obtained within a band corresponding to a half period of the FSR, and the slope of the group delay characteristic (that is, the dispersion value) increases as the number of layers increases. Can be set larger. Therefore, the light dispersion filter of the present invention is preferably formed using an etalon resonator having three or more layers.

  In the above Japanese Patent Laid-Open No. 2002-122732, a reflection type dispersion compensator using an etalon resonator is described in detail. Therefore, in a dispersion compensator using an etalon resonator, it is known to set the pole value (frequency at which the transmission characteristic reaches a peak) to a desired value. However, the light dispersion filter of the present invention differs from the above publication in how to set the pole value.

  In the present invention, when forming a transmissive light dispersion filter, the pole values are set as follows. As an example, a case where the light dispersion filter is configured by a three-layer etalon resonator will be described.

  As described above, the transmission characteristics of each etalon resonator depend on the respective extreme values. Here, the extreme values are defined as p1, p2, and p3, and p1, p2, and p3 are determined so as to have a constant dispersion characteristic within a band corresponding to a half cycle of the FSR.

Since the denominator of the transmission characteristics of each etalon resonator is determined from the pole, if the propagation constant of one round of incident light in the etalon resonator is z, the denominator is
(1-p1 / z) · (1-p2 / z) · (1-p3 / z) (1)
Is proportional to

  Further, the reflectance at each boundary surface of the three-layer etalon resonator (first etalon resonator to third etalon resonator) is defined as r0, r1, r2, and r3. However, r0 is the interface between the first etalon resonator and air, r1 is the interface between the first etalon resonator and the second etalon resonator, and r2 is the second etalon resonator and the third etalon resonator. R3 is the reflectance of the interface between the third etalon resonator and the air.

At this time, the transmission characteristics of the etalon resonator are according to Equation 35 of Dowling, “Lightwave Lattice Filters for Optically Multiplexed Communication Systems”, IEEE Journal of Quantum Electronics, 1994, No. 12, vol. 3, pp.471-486. And its denominator is
r0 · r3 / z ³ + (r0 · r2 + r1 · r3 + r0 · r1 · r2 · r3) / z ² + (r0 · r1 + r1 · r2 + r2 · r3) / z + 1 (2)
Is proportional to

  Equation (1) is the transmission characteristic obtained from the pole, and equation (2) is the transmission characteristic obtained from the reflectance at each boundary surface, and the shapes of these denominators must match. Therefore, if r0 to r3 are determined so that the coefficients z in the expressions (1) and (2) are equal, the configuration of the light dispersion filter used in the present invention is determined.

The number of conditions obtained by the above coefficient comparison matches the number of layers of the etalon resonator, but the reflectance is one more than the number of surfaces of the etalon resonator, that is, the number of conditions. Therefore, r0 to r3 are determined by determining one arbitrary value, for example, p1 = 0.1 × e ⁱ π ^{/ 6} , p2 = 0.1 × e ⁻ⁱ π ^{/ 6} , In the case of p3 = 0.25, if r0 = 0.1%, r1 = 2%, r2 = 80%, and r3 = 10%. Here, when r0 is set to a value close to non-reflection, r1 to r3 have the highest reflectivity at the central boundary surface in the thickness direction of the light dispersion filter, and the reflectivity becomes lower as the boundary surface is closer to both end surfaces. I understand that. Note that the boundary surface where the reflectivity is highest is not limited to the center of the light dispersion filter, and slightly varies depending on the value of r0. Even when the number of layers of the etalon resonator is more than 3, each reflectance can be obtained by comparing the denominator coefficients of the transmission characteristics.

  Further, in the reflection type light dispersion filter, as in the transmission type, the reflectance at each boundary surface is determined by comparing the coefficient of the transmission characteristic obtained from the pole and the transmission characteristic obtained from the reflectance. In the reflection type light dispersion filter, the incident surface is set to the lowest reflectance, the reflectance of the final end surface opposite to the incident surface is set to 100%, and the reflection of each boundary surface from the incident surface toward the final end surface is performed. The rate gradually increases.

  In the light dispersion filter of the present invention, a multilayer film made of a known dielectric thin film is used as a partial reflection layer of each etalon resonator, and a substrate (light transmission layer) made of glass or semiconductor is sandwiched between the multilayer films. To do. Here, when the light dispersion filter is of a transmission type, the transmission power has a periodic characteristic with respect to the frequency as well as the dispersion characteristic, and thus the optical signal waveform may be distorted. Therefore, it is desirable that the transmission power characteristics of the multilayer film have as little dependence on the frequency (wavelength dependence) as possible. As described above, in the present invention, the reflectance of an arbitrary boundary surface in a plurality of etalon resonators can be set to a desired value, so that the reflectance of the light incident surface can be set high. In that case, since the optical power returning from the exit surface side of the light dispersion filter can be reduced, the frequency dependence of the dispersion characteristic of the light finally transmitted through the light dispersion filter can be reduced. Incidentally, this effect is remarkable when the reflectance of light on the incident surface is set to 50% or more. When the reflectance of light on the incident surface is set to be relatively high, the reflectance at each boundary surface of the light dispersion filter of the present invention gradually decreases from the incident surface toward the exit surface. Alternatively, after decreasing from the incident surface toward the exit surface, the height is once increased and then decreased toward the exit surface again.

  In the optical dispersion filter of the present invention, when the number of layers of the etalon resonator is increased, the dispersion compensation value can be further increased, and the operation band can be widened. However, when the number of layers of the etalon resonator is increased, the number of reflecting surfaces is increased, so that the light transmission power is reduced. Although the number of layers of the etalon resonator is considered to be about 20 at the maximum, an optimal number of layers may be selected in consideration of the attenuation of transmitted power and necessary dispersion characteristics.

  In addition, although the light dispersion filter of this invention calculates | requires the reflectance of each interface of an etalon resonator using said Formula (1), (2), respectively, the reflectance of each interface is calculated | required value There is no need to match exactly. An error of about ± 10% with respect to the calculated value is an allowable range in the characteristics, and the transmission characteristics do not greatly deviate if the relationship between the reflectances of the respective boundary surfaces satisfies the above conditions.

  The light dispersion filter of the present invention can also use an air layer instead of the substrate. However, since the FSR of each etalon resonator must be equal, the product of the refractive index and the thickness of the medium (substrate or air) of each substrate is set to be approximately equal. Here, the product of the refractive index and the thickness of each medium is desirably equal, but it is not necessary to be exactly equal. For example, if the thickness of each substrate is 1 mm, an error of several to several tens of microns has no effect.

  In the present invention, an adhesive (for example, an epoxy adhesive) is used as a method for joining the etalon resonators. The adhesive preferably has the same refractive index as that of the substrate. When such an adhesive is used, there is no reflection of light at the boundary between the adhesive and the substrate, and even if the thickness of the adhesive varies by several microns for each substrate, the thickness of each substrate (in the order of millimeters) Since the corresponding FSRs are almost equal, there is no problem.

  Moreover, in the light dispersion filter of the present invention, it is possible to omit at least one multilayer film provided on the incident surface or the emission surface. In that case, it is considered that the reflectance of the entrance surface or the exit surface is about 2% from the difference in refractive index between the substrate and air.

  Furthermore, in the present invention, a material such as a dielectric such as glass or a semiconductor is used as a substrate for determining the resonator length of the etalon resonator. However, if a semiconductor substrate having an amplifier circuit is formed, an optical signal to be transmitted is transmitted. Amplification is also possible.

Next, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a cross-sectional view showing a configuration of a first embodiment of the light dispersion filter of the present invention, FIG. 2 is a diagram showing a configuration example of the multilayer film shown in FIG. 1, and FIG. FIG. 6B is a cross-sectional view showing a configuration using a four-layer thin film, FIG. 10C is a cross-sectional view showing a configuration using an eight-layer thin film, and FIG. FIG. 4D is a cross-sectional view showing a configuration using 12 layers of thin films. Although FIG. 1 shows an example in which the light dispersion filter is composed of six layers of etalon resonators, the number of etalon resonators is not limited to six layers, and depends on the desired dispersion characteristics and transmittance. There may be fewer than six layers (however, three or more layers), or more.

  As shown in FIG. 1, the light dispersion filter of the first embodiment includes first to sixth substrates 26 to 26 and first to sixth substrates 26 that are alternately arranged. The first multilayer film 27 to the seventh multilayer film 33 are included.

  The first substrate 21 to the sixth substrate 26 and the first multilayer film 27 to the seventh multilayer film 33 are bonded using an adhesive. The adhesive preferably has a refractive index close to that of the first substrate 21 to the sixth substrate 26 or the first multilayer film 27 to the seventh multilayer film 33.

  The first substrate 21 to the sixth substrate 26 are formed with a thickness of 1 mm using, for example, general glass having a refractive index of 1.5 so that the FSR is 100 GHz.

  Further, when the first multilayer film 27 to the seventh multilayer film 33 are set to have different light reflectivities and form a transmissive light dispersion filter, the thickness of the light dispersion filter shown in FIG. The multilayer film closer to the boundary surface near the center in the direction (the fourth multilayer film 30 in FIG. 1) is set to a higher reflectance, and the multilayer films closer to both end faces (the first multilayer film 27 and the seventh multilayer film in FIG. 1). The multilayer film 33) is set to a lower reflectance. On the other hand, when a reflection type light dispersion filter is formed, the multilayer film on the incident surface (first multilayer film 27 in FIG. 1) has the lowest reflectivity, and the multilayer film on the final end surface opposite to the incident surface (FIG. 1 is set so that the reflectance gradually increases toward the seventh multilayer film 33).

  As shown in FIG. 2A, when forming a transmission type light dispersion filter, the first multilayer film 27 and the seventh multilayer film 33 are, for example, a low refractive index glass thin film having a refractive index of 1.2. Using the (first thin film 40), the thickness of the transmitted light is ¼ times the wavelength λ (= 1.55 μm / refractive index 1.2) in the thin film. In this embodiment, the reflectance between the air and the first substrate 21 is set to 0% by the first multilayer film 27, and the reflectance between the air and the seventh substrate 26 is set by the seventh multilayer film 33. Set to 0%.

  In the present embodiment, an example in which the first multilayer film 27 and the seventh multilayer film 33 are formed as a single-layer thin film is shown, but a low-reflection film composed of a two-layer or three-layer thin film can also be used. is there. In that case, the thickness of each thin film layer is not limited to 1/4 of the wavelength λ of transmitted light as long as a low reflection film can be formed. In the transmission type light dispersion filter of this embodiment, the multilayer film closer to the central boundary surface has a higher light reflectance, and thus the first multilayer film 27 and the seventh multilayer film 33 have the second reflectance. If the reflectance is not higher than that of the multilayer film 28 and the sixth multilayer film 32, it is not necessary to limit to 0%. For example, the reflectance at the interface between air and the first substrate 21 or the sixth substrate 26 is 2%. Therefore, if the above reflectance condition is satisfied, the first multilayer film 27 and the seventh multilayer film 33 are used. Is not necessary.

  When a reflective light dispersion filter is formed, only the reflectance of the first multilayer film 27 is set to 0%, for example. In the case of the reflective type as well, the reflectance value of the first multilayer film 27 need not be limited to the above value as in the case of the transmissive type. It may be.

As shown in FIG. 2B, when forming a transmission type light dispersion filter, the second multilayer film 28 and the sixth multilayer film 32 are, for example, four thin films (first thin film 41 to first thin film). 4 thin film 44). Here, SiO ₂ (silicon dioxide) having a refractive index of 1.5 is used for the first thin film 41 and the third thin film 42, and a refractive index of ₂ is used for the second thin film 43 and the fourth thin film 44. .8 TiO (titanium oxide) is used. With such a configuration, the reflectance of the second multilayer film 28 and the sixth multilayer film 32 is set to 20%.

  In this embodiment, the reflectance of the second multilayer film 28 and the sixth multilayer film 32 is set to 20%. However, the multilayer film closer to the central boundary surface in the thickness direction of the light dispersion filter has a light reflectance. Therefore, if the reflectances of the second multilayer film 28 and the sixth multilayer film 32 are not higher than the reflectances of the third multilayer film 29 and the fifth multilayer film 31, they are set to 20%. There is no need to limit. The second multilayer film 28 and the sixth multilayer film 32 are not limited to four layers as long as the reflectance condition is satisfied. Further, the thickness of each thin film can be freely set as long as the above reflectance condition is satisfied.

  On the other hand, when forming a reflection type light dispersion filter, for example, the reflectance of the second multilayer film 28 is set to 20% using four thin films. Also in the case of the reflective type, the reflectance of the second multilayer film 28 does not need to be limited to the above value as in the case of the transmissive type, and any number of layers can be used as long as the configuration of the multilayer film satisfies the above reflectance condition. Good.

As shown in FIG. 2C, when the transmission type light dispersion filter is formed, the third multilayer film 29 and the fifth multilayer film 31 are composed of eight thin films (first thin film 45 to eighth thin film). The thin film 52) is used to form a laminated film. Here, SiO ₂ (silicon dioxide) having a refractive index of 1.5 is used for the first thin film 45, the third thin film 46, the fifth thin film 47, and the seventh thin film 48, and the second thin film. 49, the fourth thin film 50, the sixth thin film 51, and the eighth thin film 52 are made of TiO (titanium oxide) having a refractive index of 2.8. With such a configuration, the reflectance of the third multilayer film 29 and the fifth multilayer film 31 is set to 40%.

  The reflectivity of the third multilayer film 29 and the fifth multilayer film 31 need not be limited to 40% unless the reflectivity of the fourth multilayer film 30 is higher. Further, the third multilayer film 29 and the fifth multilayer film 31 are not limited to eight layers as long as the above reflectance condition is satisfied. Further, the thickness of each thin film can be freely set as long as the above reflectance condition is satisfied.

  On the other hand, when forming a reflection type light dispersion filter, for example, the reflectance of the third multilayer film 29 is set to 40% using eight thin films. Also in the case of the reflective type, the reflectance values of the third multilayer film 29 and the fifth multilayer film 31 do not need to be limited to the above values as in the transmissive type, and the configuration of the multilayer film also satisfies the reflectance conditions. Any number of layers may be used as long as it is satisfied.

As shown in FIG. 2D, the fourth multilayer film 30 is formed using a laminated film composed of 12 layers of thin films (the first thin film 53 to the twelfth thin film 64). Here, the first thin film 53, the third thin film 54, the fifth thin film 55, the seventh thin film 56, the ninth thin film 57, and the eleventh thin film 58 are made of SiO ₂ having a refractive index of 1.5. (Silicon dioxide) is used, and the second thin film 59, the fourth thin film 60, the sixth thin film 61, the eighth thin film 62, the tenth thin film 63, and the twelfth thin film 64 have a refractive index of 2. .8 TiO (titanium oxide) is used. With such a configuration, the reflectance of the fourth multilayer film 30 is set to 80%.

  In the configuration of the transmission type light dispersion filter of the present embodiment, the fourth multilayer film 30 serves as a central boundary surface. Therefore, if the reflectance of the fourth multilayer film 30 can be set to the highest, the reflectance is 80%. There is no need to limit. The fourth multilayer film 30 is not limited to 12 layers as long as the above reflectance condition is satisfied. Further, the thickness of each thin film can be freely set as long as the above reflectance condition is satisfied.

  On the other hand, in the case of forming a reflection type light dispersion filter, for example, the reflectance of the fourth multilayer film 30 is set to 50% using 10 thin films. In the case of the reflective type, the reflectance of the fourth multilayer film 30 does not need to be limited to the above value as in the case of the transmissive type, and any number of layers can be used as long as the configuration of the multilayer film satisfies the above reflectance condition. Good. In the case of the reflection type, for example, the fifth multilayer film 31 uses 10 layers of thin film and the reflectance is set to 60%, and the sixth multilayer film 32 uses 12 layers of thin film and has a reflectance of 80%. %, And the seventh multilayer film 33 is formed of 12 or more thin films and the reflectance is set to 100%. These multilayer films are not limited in the number of layers as long as the above reflectance condition is satisfied, and the thickness of each thin film can be freely set as long as the above reflectance condition is satisfied.

  In this embodiment, when a transmission type light dispersion filter is formed, the reflectance of the multilayer film is set to be symmetric from the center boundary surface of the light dispersion filter toward both ends. It is not necessary to be symmetric as long as the reflectance at the boundary surface is the highest.

  In the present embodiment, the first substrate 21 to the sixth substrate 26 are made of glass having the same refractive index. However, the refractive index and thickness of each etalon resonator are set so that the FSRs are equal. The first substrate 21 to the sixth substrate 26 may be made of different materials as long as the products of the lengths are equal.

  In this embodiment, an optical dispersion filter composed of six-layer etalon resonators is shown. However, as shown in FIG. 3, increasing the number of layers of etalon resonators increases the dispersion compensation value. It is possible to widen the operating band. As described above, when the number of layers of the etalon resonator is increased, the number of reflection surfaces is increased, so that the light transmission power is reduced. Therefore, the optimum number of layers is selected in consideration of the attenuation amount of the transmission power and necessary dispersion characteristics.

As shown in FIG. 4, the light dispersion filter of the present embodiment has a group delay characteristic in which a peak appears every 100 GHz. The value obtained by differentiating the group delay characteristic in FIG. 4 with respect to the wavelength is dispersion. By using the characteristic part that rises to the right of the graph shown in FIG. 4, a dispersion characteristic of 300 psec / nm can be obtained in the range of 30 GHz. Similarly, a dispersion characteristic of −300 psec / nm can be obtained in the range of 30 GHz by using the characteristic part that descends to the right. This means that the dispersion experienced in an optical fiber of approximately 20 km can be compensated.
(Second embodiment)
FIG. 5 is a sectional view showing the configuration of a second embodiment of the light dispersion filter of the present invention.

  As shown in FIG. 5, the light dispersion filter of the second embodiment has a configuration in which a plurality of etalon resonators (four in FIG. 5) are separated from each other and arranged in series.

  As in the first embodiment, the etalon resonator includes a multilayer film (first multilayer) bonded to a substrate made of a dielectric or semiconductor (first substrate 71 to fourth substrate 74) and sandwiching the substrate. Film 75 to eighth multilayer film 82).

The substrate is formed with a thickness of 1 mm using, for example, general glass having a refractive index of 1.5 so that the FSR is 100 GHz. The multilayer film has a structure in which a SiO ₂ (silicon dioxide) thin film or a TiO (titanium oxide) thin film is laminated as in the first embodiment. In this embodiment, the etalon resonators are arranged with an interval of 1.5 mm so that the FSR becomes 100 GHz corresponding to the refractive index of air 1.0.

  Also in the light dispersion filter of the present embodiment, as in the first embodiment, in the case of the transmission type, the reflectance of the multilayer film of each etalon resonator is the highest in the multilayer film used in the etalon resonator near the center. Set to lower toward both ends. Specifically, the reflectance of light by the first multilayer film 75 and the eighth multilayer film 82 is 0%, the reflectance of light by the second multilayer film 76 and the seventh multilayer film 81 is 20%, The light reflectance of the third multilayer film 77 and the sixth multilayer film 80 is set to 40%, and the light reflectance of the fourth multilayer film 78 and the fifth multilayer film 79 is set to 80%.

  In the case of the reflection type, the reflectance of the incident surface (first multilayer film 75 in FIG. 5) is the lowest (for example, 0%), and the final end surface opposite to the incident surface (eighth multilayer in FIG. 5). The film 82) is set to be the highest (for example, 100%).

  In the present embodiment, as in the first embodiment, the reflectance value may be set in any way as long as the relationship of the reflectance of each multilayer film is set so as to satisfy the above condition.

The dispersion compensation value realized by the transmission type light dispersion filter of this example was 400 psec / nm. This means that the dispersion experienced in an optical fiber of approximately 25 km can be compensated.
(Third embodiment)
FIG. 6 is a sectional view showing the configuration of the third embodiment of the light dispersion filter of the present invention.

  As shown in FIG. 6, in the light dispersion filter of the third embodiment, as in the second embodiment, a plurality of etalon resonators (four in FIG. 6) are arranged apart from each other in series, and each etalon resonator is A gap substrate (first gap substrate 131 to third gap substrate 133) for controlling the space between the air layers is inserted therebetween. The first gap substrate 131 to the third gap substrate 133 are each formed using a material that does not transmit light (for example, metal). Since other configurations are the same as those of the second embodiment, description thereof is omitted.

According to the configuration of the light dispersion filter of this embodiment, the distance between the etalon resonators constituting the air layer can be easily set using the gap substrate. In such a configuration, if a material having a large coefficient of thermal expansion is used as the gap substrate, it is possible to easily change the transmission characteristics and the dispersion amount by changing the ambient temperature.
(Fourth embodiment)
FIG. 7 is a cross-sectional view showing the configuration of the fourth embodiment of the light dispersion filter of the present invention.

  The light dispersion filter of the fourth embodiment has a configuration in which a plurality of etalon resonators are stacked as in the first embodiment (five layers in FIG. 7), and each substrate (the first in FIG. 7 determines the etalon resonator length). In this configuration, the medium of the first substrate 150 to the fifth substrate 154) is changed, and these are directly bonded with an adhesive.

  In this embodiment, for example, glass having a light refractive index of 1.5 is used as the first substrate 150 and the fifth substrate 154, and a light refractive index of 2 is used as the second substrate 151 and the fourth substrate 153. ZnO (zinc oxide) is used, and TiO (titanium oxide) having a refractive index of light of 2.8 is used as the third substrate 152. Note that coating films 155 and 156 having low reflectivity may be formed at the interfaces between the first substrate 150 and the fifth substrate 154 and air.

  In general, light is reflected at the boundary where the refractive index of a substance changes. Therefore, if a plurality of substrates having different refractive indexes are prepared and bonded together as in this embodiment, there is no need to provide a multilayer film on the interface between the substrates. At this time, the reflectance at the boundary surface of each substrate is reflected at the boundary surface near the center in the thickness direction of the light dispersion filter, for example, when a transmissive light dispersion filter is formed, as in the first embodiment. What is necessary is just to select the refractive index of each board | substrate so that a rate may be the highest and a reflectance may become low toward both ends. In the case of forming a reflection type light dispersion filter, the refractive index of each substrate may be selected so that the reflectance gradually increases from the light incident surface toward the final end surface on the opposite side.

According to the configuration of the light dispersion filter of the present embodiment, the multilayer film constituting each etalon resonator is not required, and the material for forming the multilayer film, and the time and equipment required for manufacturing are not required. The cost of the light dispersion filter can be reduced.
(5th Example)
FIG. 8 is a sectional view showing the configuration of the fifth embodiment of the light dispersion filter of the present invention.

  The light dispersion filter of the fifth embodiment has a configuration in which a reflecting mirror 160 for totally reflecting the light emitted from the light dispersion filter is added to the light dispersion filter of the first embodiment.

  The reflecting mirror 160 is installed at a position where the distance between the exit surface and the refractive index of the medium (for example, air) between the exit surface and the thickness of the substrate of the etalon resonator × 1/2 of the refractive index. Is done.

In such a configuration, the optical signal emitted from the light dispersion filter passes through the light dispersion filter twice. For example, in the light dispersion filter according to the first embodiment shown in FIG. 1, when the final end surface opposite to the light incident surface is totally reflected, the light reflected and emitted toward the incident surface in each etalon resonator is emitted. The amount of dispersion compensation is reduced by interference with the light reflected by the surface. By returning the light from the emission surface using a reflecting mirror as in the present embodiment, it is possible to obtain a larger dispersion compensation amount than the configuration in which total reflection is performed at the final end face of the etalon resonator.
(Sixth embodiment)
FIG. 9 is a sectional view showing the configuration of the sixth embodiment of the light dispersion filter of the present invention.

  The light dispersion filter of the sixth embodiment has a configuration in which a semiconductor is used as a substrate of an etalon resonator, and an optical waveguide 162 and an optical amplifier circuit for amplifying an optical signal are formed on the semiconductor substrate 161.

  The optical amplifier circuit uses, for example, well-known stimulated emission light, and has a plurality of diffraction gratings (first diffraction grating 163 to fifth diffraction grating 167 in FIG. 9) for each predetermined distance on the optical waveguide. It is the structure which formed. Note that coating films 168 and 169 having low reflectivity may be formed at the interface between the semiconductor substrate 161 and air. Since the diffraction grating has a higher reflectance as the number of grating periods increases, the reflectance of the diffraction grating near the center of the optical waveguide 162 (the third diffraction grating 165 in FIG. 9) is set to be the highest, If the reflectance of the diffraction grating is set to be lower, a transmissive light dispersion filter is obtained. In addition, the first diffraction grating 163 on the light incident surface side is set to have the smallest number of periods and the fifth diffraction grating 167 is set to have the largest number of periods, and is provided on the final end surface on the opposite side to the incident surface. If the reflectance of the multilayer film is set to a high reflectance (for example, 100%), a reflective light dispersion filter is obtained.

According to the light dispersion filter of this example, since a semiconductor having a refractive index of about 3.5 is used as the substrate of the etalon resonator, the element length can be formed shorter than the configuration using glass having a refractive index of 1.5. Further, since it has an optical amplification function, it can compensate for the coupling loss with the optical fiber.
(Seventh embodiment)
In the seventh embodiment, an optical module using a transmissive light dispersion filter among the light dispersion filters described in the first to sixth embodiments is proposed.

  FIG. 10 is a cross-sectional view showing one configuration example of an optical module using the transmission type light dispersion filter of the present invention.

  As shown in FIG. 10, the optical module 1 of the present embodiment is configured to incorporate the transmission type light dispersion filter 3 described in the first to sixth embodiments. 4 is used as a dispersion compensator for compensating for dispersion caused by 4.

  When the optical module is a transmission module that transmits an optical signal, the optical module 1 includes an optical active element 2 that is a light source, and uses the light dispersion filter 3 of the present invention for the light emitted from the optical active element 2. After the dispersion opposite to the dispersion by the optical fiber 4 is given, the dispersion is introduced into the optical fiber 4.

  When the optical module is a receiving module that receives an optical signal, the optical module 1 includes an optical active element 2 that is a light receiving element, and the optical dispersion filter 3 of the present invention is applied to the optical signal transmitted through the optical fiber 4. Is applied to the optical active element 2 after giving a dispersion opposite to the dispersion received by the optical fiber 4.

  In the optical module of this embodiment, since the light dispersion filter 3 is a transmission type, the light dispersion filter 3 is disposed on the optical axis connecting the optical fiber 4 and the optical active element 2.

  The optical module 1 shown in FIG. 10 shows only the light active element 2 and the light dispersion filter 3 which are light sources or light receiving elements. However, the light emitted from the light active element 2 is transmitted to the light dispersion filter 3. A lens for condensing light and a lens for condensing the light transmitted through the light dispersion filter 3 in the core of the optical fiber 4 may be provided. Or you may provide the lens for condensing the light radiate | emitted from the optical fiber 4 to the light dispersion filter 3, and the lens for condensing the light which permeate | transmitted the light dispersion filter 3 to the optical active element 2. FIG. Further, an optical isolator may be provided between the light source and the light dispersion filter 3 in order to prevent reflected light from the light dispersion filter 3 from returning to the light source and disturbing oscillation.

Since the light dispersion filter of the present invention can be formed smaller than conventional dispersion compensators, for example, it can be incorporated in an optical module including a direct modulation semiconductor laser or an external modulation semiconductor laser as a light source. It becomes possible. Therefore, since the dispersion characteristic that compensates the dispersion received by the optical fiber can be provided in the optical module, the transmission distance of the optical communication system using the optical fiber without providing a large-scale dispersion compensator outside the optical module. Can be expanded.
(Eighth embodiment)
In the eighth embodiment, an optical module using a reflective light dispersion filter among the light dispersion filters described in the first to sixth embodiments is proposed.

  FIG. 11 is a cross-sectional view showing a configuration example of an optical module using the reflection type light dispersion filter of the present invention.

  As shown in FIG. 11, the optical module 11 of the present embodiment has a configuration in which the reflection type light dispersion filter 13 described in the first to sixth embodiments is incorporated, and the light dispersion filter 13 is an optical fiber. 14 is used as a dispersion compensator for compensating for the dispersion caused by 14.

  When the optical module is a transmission module that transmits an optical signal, the optical module 11 includes an optical active element 12 that is a light source, and uses the light dispersion filter 13 of the present invention for the light emitted from the optical active element 12. After the dispersion opposite to the dispersion by the optical fiber 14 is given, the dispersion is introduced into the optical fiber 14.

  When the optical module is a receiving module that receives an optical signal, the optical module 11 includes an optical active element 12 that is a light receiving element, and the optical dispersion filter 13 of the present invention is applied to the optical signal transmitted through the optical fiber 14. Is applied to the optical active element 12 after giving a dispersion opposite to the dispersion received by the optical fiber 14.

  In the optical module of this embodiment, since the light dispersion filter 13 is a reflection type, the optical active element 12 is disposed at a position shifted from the optical axis connecting the optical fiber 14 and the light dispersion filter 13. By disposing the optical active element 12 at such a position, an element (circulator) for changing the optical path of incident light or outgoing light becomes unnecessary, and therefore, the increase in the size of the optical module can be prevented.

  Also in the optical module of the present embodiment, the light emitted from the optical active element 12 and the light reflected by the light dispersion filter 13 are collected in the core of the optical fiber 14 to collect the light on the light dispersion filter 13. A lens for emitting light may be provided. Alternatively, a lens for condensing the light emitted from the optical fiber 14 on the light dispersion filter 13 and a lens for condensing the light reflected by the light dispersion filter 13 on the optical active element 12 may be provided. Furthermore, an optical isolator may be provided between the light source and the light dispersion filter 13 in order to prevent reflected light from the light dispersion filter 13 from returning to the light source and disturbing oscillation.

Similar to the seventh embodiment, the optical module of this embodiment can be incorporated in an optical module including a direct modulation semiconductor laser, an external modulation semiconductor laser, or the like, which is a light source, for example. Therefore, since the dispersion characteristic that compensates the dispersion received by the optical fiber can be provided in the optical module, the transmission distance of the optical communication system using the optical fiber without providing a large-scale dispersion compensator outside the optical module. Can be expanded.
(Ninth embodiment)
The ninth embodiment proposes another configuration example of an optical module using a reflective light dispersion filter among the light dispersion filters described in the first to sixth embodiments.

  FIG. 12 is a cross-sectional view showing another configuration example of the optical module using the reflection type light dispersion filter of the present invention.

  As shown in FIG. 12, the optical module 100 of the present embodiment is configured to incorporate the reflection type light dispersion filter 102 described in the first to sixth embodiments, and the light dispersion filter 102 is used as an optical fiber. It is used as a dispersion compensator for compensating for the dispersion due to 104.

  When the optical module is a transmission module that transmits an optical signal, the optical module 100 includes an optical active element 101 that is a light source, and uses the light dispersion filter 102 of the present invention for the light emitted from the optical active element 101. After the dispersion opposite to the dispersion by the optical fiber 104 is given, the dispersion is introduced into the optical fiber 104.

  When the optical module is a receiving module that receives an optical signal, the optical module 100 includes an optical active element 101 that is a light receiving element, and the optical dispersion filter 102 of the present invention is applied to the optical signal transmitted through the optical fiber 104. Is applied to the optical active element 101 after giving a dispersion opposite to the dispersion received by the optical fiber 104.

  Further, the optical module 100 of this embodiment includes a half mirror 103 disposed on the optical axis connecting the optical fiber 104 and the light dispersion filter 102, and the optical active element 101 is on the optical axis of the reflected light of the half mirror 103. Placed in.

  In such a configuration, since the optical signal passes through the half mirror 103 twice, the power of the light emitted from the optical active element 101 or the light received through the optical fiber 104 is reduced to ¼.

However, unlike the circulator or the like, the half mirror 103 is small enough to be housed in the optical module 100, and is therefore incorporated in an optical module including a direct modulation semiconductor laser or an external modulation semiconductor laser as a light source. It becomes possible. Therefore, as in the seventh and eighth embodiments, since dispersion characteristics for compensating for dispersion received by the optical fiber can be provided in the optical module, a large-scale dispersion compensator is not provided outside the optical module. The transmission distance of an optical communication system using an optical fiber can be increased.
(Tenth embodiment)
The tenth embodiment is a modification of the optical module shown in the seventh to ninth embodiments.

  FIG. 13 is a cross-sectional view showing a first modification of the optical module using the light dispersion filter of the present invention.

  As shown in FIG. 13, the tenth embodiment includes a first temperature controller 93 for controlling the temperature of the optical active element in the optical modules shown in the seventh to ninth embodiments, and an optical dispersion. This is a configuration having a second temperature control device 94 for controlling the temperature of the filter. The first temperature control device 93 and the second temperature control device 94 include, for example, a heater (not shown), a current source that supplies current to the heater, a temperature sensor that detects the temperature of the light active element and the light dispersion filter, and The controller has a controller that turns on / off the current supplied to the heater according to the detection value of the temperature sensor.

  FIG. 12 shows the configuration of the optical module having the transmission type light dispersion filter shown in the seventh embodiment as an example, but the reflection type light dispersion filter as in the eighth and ninth embodiments. This embodiment can also be applied to a configuration having

In general, the temperature change rate of the wavelength corresponding to the optical active element is about 0.08 nm / ° C., and the temperature change rate of the light dispersion filter is 0.01 nm / ° C. Therefore, by independently controlling the temperature of the optical active element and the light dispersion filter using the first temperature control device 93 and the second temperature control device 94, each can be changed to a desired characteristic. Note that the dispersion amount of the light dispersion filter changes with the wavelength when the temperature changes. Since the amount of change in dispersion varies depending on the medium used in the light dispersion filter, the number of layers, and the like, it may be designed to have an optimum value.
(Eleventh embodiment)
The eleventh embodiment is another modification of the optical module described in the seventh to tenth embodiments.

  FIG. 14 is a cross-sectional view showing a second modification of the optical module using the light dispersion filter of the present invention.

  As shown in FIG. 14, the eleventh embodiment has a configuration in which an optical fiber can be removed from the optical module 110 incorporating the light dispersion filter of the present invention shown in the seventh to tenth embodiments. For example, the optical connector 113 is fixed to the optical fiber attachment portion. FIG. 14 shows an example of the configuration of the optical module having the transmission type light dispersion filter shown in the seventh embodiment, but the reflection type light dispersion filter as in the eighth and ninth embodiments. This embodiment can also be applied to a configuration having the first and second temperature control devices as in the tenth embodiment.

In such a configuration, since the cost of the optical module 110 can be reduced, an optical module suitable for low-end use can be obtained.
(Twelfth embodiment)
The twelfth embodiment proposes an optical dispersion measuring device to which the optical dispersion filter described in the first to sixth embodiments is applied.

  FIG. 15 is a block diagram showing a configuration example of an optical dispersion measuring device using the optical dispersion filter of the present invention.

  As shown in FIG. 15, the twelfth embodiment is an optical dispersion measuring instrument for measuring the amount of dispersion using an optical dispersion filter.

  The optical dispersion measuring device includes an optical demultiplexer 124 that divides an optical signal, an optical dispersion filter 121 through which one optical signal demultiplexed by the optical demultiplexer 124 passes, and an optical signal that has passed through the optical dispersion filter 121. A first optical receiver 122 that outputs an electrical signal corresponding to the optical signal, a second optical receiver 123 that outputs an electrical signal corresponding to the other optical signal demultiplexed by the optical demultiplexer 124, and a first And a signal difference circuit 125 for outputting a difference between signals output from the second optical receiver 122 and the second optical receiver 123.

In such a configuration, since the output value of the signal difference circuit 125 is proportional to the dispersion value by the light dispersion filter 121, the dispersion amount of the light dispersion filter 121 can be obtained. Further, when the dispersion amount of the light dispersion filter 121 is known in advance, the dispersion amount of the optical signal input to the light dispersion measuring device can be measured from the difference from the dispersion amount.
(Thirteenth embodiment)
The thirteenth embodiment proposes a communication channel extracting device to which the optical dispersion filter described in the first to sixth embodiments is applied.

  FIG. 16 is a waveform diagram showing the effect of the communication channel extracting apparatus using the light dispersion filter of the present invention.

  Generally, the frequency interval of each communication channel in a WDM optical communication system is standardized at 50 GHz, 100 GHz, or the like.

  As described above, the transmission type light dispersion filter of the present invention has a wavelength region through which light is most transmitted every FSR period. Therefore, by setting the FSR of the optical dispersion filter of the present invention to the channel interval of the WDM optical communication system <the FSR of the optical dispersion filter, communication channel extraction for selecting the communication channel of the WDM optical communication system that has passed through the optical dispersion filter It can be used as a device.

  Specifically, the FSR of the light dispersion filter is increased by about 10 to 20% from the channel interval, for example, 60 GHz and 120 GHz. At this time, if the temperature of the light dispersion filter is changed using the temperature control device shown in the tenth embodiment, the FSR of the light dispersion filter changes, so that the desired WDM optical communication system has a plurality of communication channels. It is possible to extract only the optical signals of the communication channels.

1, 11, 100, 110 Optical module 2, 12, 101 Optical active element 3, 13, 102, 121 Optical dispersion filter 4, 14, 104 Optical fiber 21, 71, 150 First substrate 22, 72, 151 Second Substrate 23, 73, 152 Third substrate 24, 74, 153 Fourth substrate 25, 154 Fifth substrate 26 Sixth substrate 27, 75 First multilayer film 28, 76 Second multilayer film 29, 77 Third multilayer film 30, 78 Fourth multilayer film 31, 79 Fifth multilayer film 32, 80 Sixth multilayer film 33, 81 Seventh multilayer film 82 Eighth multilayer film 40, 41, 45, 53 1st thin film 43, 49, 59 2nd thin film 42, 46, 54 3rd thin film 44, 50, 60 4th thin film 47, 55 5th thin film 51, 61 6th thin film 48, 56 4th 7th thin film 52, 62 8th thin film 57 9th thin film 63 10th thin film 58 11th thin film 64 11th thin film 93 1st temperature control device 94 2nd temperature control device 103 Half mirror 113 Optical connector 122 1st optical receiver 123 2nd Optical receiver 124 optical demultiplexer 125 signal difference circuit 131 first gap substrate 132 second gap substrate 133 third gap substrate 134 fourth gap substrate 155, 156, 168, 169 coating film 160 reflecting mirror 161 Semiconductor substrate 162 Optical waveguide 163 1st diffraction grating 164 2nd diffraction grating 165 3rd diffraction grating 166 4th diffraction grating 167 5th diffraction grating

Claims (6)

An optical fiber that is an optical signal transmission medium;
A reflection type light dispersion filter comprising a plurality of light transmission layers through which light is transmitted in order to compensate for dispersion received by the optical fiber, and partial reflection layers alternately arranged with the light transmission layers;
An optical active element disposed at a position avoiding an optical axis connecting the optical fiber and the light dispersion filter;
A half mirror located on the optical axis connecting the optical fiber and the light dispersion filter, and arranged so that the optical active element is located on the optical axis of the reflected light;
An optical module. The optical module of claim 1 having an optical connector for detachably securing the optical fiber. A first temperature control device for controlling the temperature of the photoactive element;
A second temperature control device for controlling the temperature of the light dispersion filter;
Light module according to claim 1 or 2, wherein having. Said optical active element, an optical module according to any one of claims 1 to 3 which is a light source for emitting light signals. Said optical active element, an optical module according to any one of claims 1 to 4 which is a light receiving element for receiving the light signal. An optical demultiplexer for dividing the optical signal;
The optical module according to claim 1, wherein one optical signal demultiplexed by the optical demultiplexer is incident;
A first optical receiver that is the optical active element that outputs an electrical signal corresponding to an optical signal incident on the optical module;
A second optical receiver that outputs an electrical signal corresponding to the other optical signal demultiplexed by the optical demultiplexer;
A signal difference circuit for outputting a difference between signals output from the first optical receiver and the second optical receiver;
A light dispersion measuring instrument.

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