JP2007003782A - Optical demultiplexer and wavelength multiplexing optical transmission module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical demultiplexer that is compact and excellent in wavelength separation characteristics even when an optical fiber with a large numerical aperture is used. <P>SOLUTION: A wavelength multiplexing light beam made incident from an optical fiber 10 reflects on a prism 16a, changes an optical path and is made incident on a concave mirror 14 of a cylindrical shape. A light beam 42 reflected by the concave mirror 14 is propagated through an optical block 18, made incident on a chirped diffraction grating 12, diffracted to a different angle by the wavelength, and converged. A light beam 43 reflected by the chirped diffraction grating 12 is reflected by a prism 16b and then optically coupled with the incident end 44 of a light receiving optical waveguide 28. A light incident part and a light exiting part are separated by providing a prism 16 and made to be positioned facing each other across the prism 16. The propagation through the optical block 18 enables the optical demultiplexer to be compact, and an aberration produced in the chirped diffraction grating can be reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical device that separates a plurality of wavelengths for each wavelength, and more particularly, to an optical demultiplexer and a wavelength multiplexing optical transmission module that demultiplexes a wavelength multiplexed optical signal transmitted using an optical fiber by a diffraction grating. Is.

  In Patent Document 1 below, a case having an internal space and a light incident port and a light output port connected to the internal space, an incident light transmission path connected to the light incident port of the case, and a light output port of the case are connected. A plurality of outgoing optical transmission lines, and a first wavelength reflection light that is provided in the internal space of the case and reflects the wavelength division multiplexed light that has entered the internal space through the incident optical transmission path to form parallel light. Wavelength division multiplexed light fixed on the concave reflection surface and the case and converted into parallel light on the first concave reflection surface at a planar reflection diffraction surface in which a plurality of linear diffraction grooves are arranged at equal intervals And a second concave reflecting surface provided in the internal space of the case for allowing the light dispersed in the grating to enter the outgoing optical transmission line, and a light incident port and light. The exit is a grating In the direction of extension of the definitive diffraction grooves, optical demultiplexer-multiplexer which is provided across the grating is disclosed.

  The following Patent Document 2 has an unequal periodic plane diffraction grating having at least two diffractive actions and a condensing action, and the light diffracted by the first diffraction grating is guided to the second diffraction grating. An optical communication duplexer configured to be further diffracted by the diffraction grating is disclosed.

  Here, the optical demultiplexer disclosed in Patent Document 1 below uses an integrated structure in which a lens system using a diffraction grating and a concave reflecting surface and an optical transmission medium are integrated. The concave reflecting surface has a function of collimating the light beam incident from the optical fiber, irradiating the diffraction grating, and condensing the parallel light beam diffracted from the diffraction grating onto the light emitting portion.

  However, when the light beam is incident on the diffraction grating as parallel light in this way, the light beam incident on the diffraction grating becomes circular, so that the area of the light beam irradiated on the diffraction grating increases. For this reason, it is necessary to increase the size of the optical demultiplexing / multiplexing unit according to the size of the diffraction grating.

  Further, since the light incident part and the light emitting part are on the same side, it is difficult to directly enter and exit the light beam. In Patent Document 1 below, an incident optical transmission line and an outgoing optical transmission line, specific examples For example, an optical fiber was used to enter and exit a light beam.

  Further, in Patent Document 2 below, a light beam is confined in an optical waveguide, and demultiplexing is performed using an unequal periodic planar diffraction grating, a so-called chirped diffraction grating.

  However, optical signals with different wavelengths can be separated with high resolution using an optical waveguide only when a single-mode light beam is incident. If a multi-mode light beam needs to be used, a diffraction grating can be used. Since the diffraction angle changes depending on the incident angle, the resolution is lowered, and sufficient wavelength separation characteristics cannot be obtained.

  Also, since two chirped diffraction gratings are used, the light incident part and the light emitting part can be in different directions, but it is difficult to increase the diffraction efficiency of the diffraction gratings when two diffraction gratings are used, There was a problem that optical loss increased.

Patent Documents 3 and 4 disclose an optical waveguide in which a core is formed by irradiating UV light, and an optical waveguide forming method.
JP 2004-29298 A Japanese Patent Laid-Open No. 61-223711 Japanese Patent Laid-Open No. 2002-258077 JP 2004-258493 A

  The present invention is an optical demultiplexer that is small in size, facilitates connection of optical components to a light incident portion and a light emission portion, and has good wavelength separation characteristics even when light is incident using an optical transmission medium having a large numerical aperture. And realizing a wavelength division multiplexing optical transmission device using the optical demultiplexer.

  An optical demultiplexer according to the present invention irradiates a light incident portion on which a wavelength-multiplexed light beam is incident, an optical path for transmitting the light beam incident on the light incident portion, and the light beam transmitted on the optical path. In the optical demultiplexer having a diffraction grating for separating an optical signal for each wavelength and a light emitting part for extracting the separated optical signal, a first optical path for bending the light beam incident from the light incident part The optical path conversion member, a concave mirror having a light collecting property in a uniaxial direction so as to reduce a divergence angle in the groove direction of the diffraction grating, and the light beam whose uniaxial divergence angle is reduced by the concave mirror. The diffraction grating having light condensing property in a uniaxial direction different from the condensing axis of the concave mirror, and a second optical path conversion member that bends the optical path of the light beam reaching the light emitting portion, The light incident part and the light emitting part are in front of each other. Characterized in that it is arranged such that the first optical path converting member or the second optical path converting members come.

  The optical demultiplexer according to the present invention includes a light incident portion on which a wavelength-multiplexed light beam is incident, an optical path for transmitting the light beam incident on the light incident portion, and the light beam transmitted on the optical path. An optical path conversion member that bends the optical path of the light beam in the optical path in an optical demultiplexer having a diffraction grating that irradiates and separates an optical signal for each wavelength, and a light emitting section that extracts the separated optical signal And a concave mirror having a light condensing property in a uniaxial direction so as to reduce a divergence angle in the groove direction of the diffraction grating, and the light beam whose divergence angle is reduced by the concave mirror is the condensing axis of the concave mirror Irradiating the diffraction grating having light condensing property in a uniaxial direction different from the above, and using the optical path changing member, the traveling direction of the light beam incident from the light incident portion and the light exiting from the light emitting portion With the direction of travel of the light beam Degrees is characterized by being arranged such that the 90 ° or higher.

  The optical path through which the light beam passes can be formed entirely by a transparent optical member, or an optical path that propagates in the air can be provided. As the diffraction grating having light condensing property, a chirp type formed on a substantially flat surface can be used.

  The blaze angle at the center of the diffraction grating is preferably 21 ° or more and 34 ° or less, and the ratio of the grating constant of the diffraction grating to the wavelength used is preferably 0.88 or more and 1.41 or less.

  A multimode optical transmission medium is preferably used as the optical transmission medium connected to the light incident portion. The light emitting part preferably has an optical waveguide.

  At this time, the best image point position where the light beam having the longest wavelength in the wavelength range incident as the light beam is collected by the diffraction grating and the position where the light beam is collected by the concave mirror are substantially equal, and the incident light enters the optical waveguide. It is preferable to come on the end face. Further, it is preferable that the optical waveguide is disposed substantially parallel to the light beam entering and exiting the diffraction grating.

  Still further, in the case of providing an amplification circuit that receives a light beam from the optical waveguide with an optical detector and amplifies an electric signal from the optical detector, the amplification circuit is provided on the substrate on which the optical waveguide is formed or the optical waveguide. It is preferable to provide it on a circuit board arranged substantially parallel to the waveguide.

  The optical demultiplexer of the present invention can be applied to a wavelength division multiplexing optical receiver module or a wavelength division multiplexing optical transmission module. In that case, a multipath is provided between the signal transmission optical fiber and the junction of the optical demultiplexer. The mode optical transmission medium can be used for connection, and the signal transmission optical fiber and the optical multiplexer can be connected using a single mode optical transmission medium.

  In the optical demultiplexer according to the present invention, the incident / exit positions of the light beam are separated by using an optical path conversion member that bends the optical path by reflecting or refracting the optical path, so that the optical component can be easily connected to the light incident part and the light output part. Can be.

  Furthermore, according to the present invention, the light beam in the uniaxial direction is collimated using a concave mirror having a light collecting property in a substantially uniaxial method and irradiated to the diffraction grating having a light collecting property. A small duplexer with good wavelength separation characteristics can be provided even if a light beam is incident using an optical transmission medium having a large numerical aperture.

  An embodiment of the present invention will be described with reference to FIGS.

  1A and 1B are diagrams for explaining an optical demultiplexer according to the present invention. FIG. 1A is a top view of the optical demultiplexer, and FIG. 1B is a side view. The light beam that has been wavelength-multiplexed and transmitted enters the optical demultiplexer 1 from the end face of the optical fiber 10 that is an optical transmission medium via the light incident part 50. This wavelength-multiplexed light beam is incident on a chirped diffraction grating 12 which is a wavelength separating means and is diffracted at different angles for each wavelength.

  The chirped diffraction grating 12 is formed with a linear grating groove parallel to the y direction on a substantially flat surface so as to diffract and collect the incident light beam 42 spreading in the xz plane. A non-uniformly spaced diffraction grating (chirped diffraction grating) with varying intervals is used. Here, a case where four wavelengths are multiplexed and separated is illustrated, but the number of wavelength multiplexing is not limited.

  The light beam incident from the optical fiber 10 is first reflected by the prism 16a as the first optical path conversion member to change the optical path, and enters the concave mirror 14. The concave mirror 14 has a so-called cylindrical shape with substantially the same cross-sectional shape in the x direction, and the divergence angle of the light beam 42 is reduced only in one axis in the y direction (the direction of the engraving line of the grating grooves) to obtain substantially parallel light. It is a reflection.

  In the x direction, even when reflected by the concave mirror 14, the same spreading angle as that before incidence is maintained. The light beam 42 reflected by the concave mirror 14 propagates through the optical block 18 and enters the chirped diffraction grating 12, and is diffracted at different angles depending on the wavelength.

  Further, due to the chirp effect of the chirped diffraction grating 12, the diffracted light beam 43 is diffracted so as to be condensed in the xz plane.

  After the optical signal diffracted and collected by the chirped diffraction grating 12 passes through an optical path opposite to that at the time of incidence, the optical signal is collected in one axis by the concave mirror 14 and reflected by the prism 16b as the second optical path conversion member. The light receiving optical waveguide 28 is optically coupled to the incident end 44.

  The light receiving optical waveguide 28 has a slab waveguide portion 38 on the incident portion side and a tapered waveguide portion 40 on the subsequent stage. The light beam 43 is condensed at the incident end 44 by the concave mirror 14 and is optically coupled to the slab waveguide portion 38 efficiently.

  The light beam 43 incident on the slab waveguide section 38 is confined in the slab waveguide 38 in the y direction and propagates, and the chirped diffraction grating 12 is collected on the surface of the slab waveguide section 38 (xz plane). Light is focused on the joint 46 with the tapered waveguide 40 provided for each wavelength band.

  The optical signal thus separated and collected enters the tapered waveguide section 40 and is detected by the photodetector array 26 having a light receiving section corresponding to each wavelength band.

  By providing the light incident portion 50 of the optical fiber 10 and the incident end face 44 of the light receiving optical waveguide 28 in the vicinity of the focal position of the concave mirror 14, parallelism in one direction (y-axis direction) of incident light using one concave mirror 14. And uniaxial focusing of diffracted light.

  Further, by providing the prism 16 as an optical path conversion member having a reflecting surface, the light incident portion and the light emitting portion are separated, and the light incident portion and the light emitting portion are positioned to face each other with the prism 16 interposed therebetween. did it.

  Therefore, in this embodiment, the traveling direction of the light beam incident from the light incident portion of the prism 16a and the traveling direction of the light beam emitted from the light exit portion of the prism 16b can be the same direction, and the light receiving optical waveguide 28 and the light detector array 26 including the photodetector array 26 can be disposed on the opposite side of the optical fiber 10 with respect to the prism 16.

  Since the light receiving section can be arranged away from the optical fiber 10, the arrangement of the demultiplexer is facilitated, and light incident on the demultiplexer 1 and light detection by the photodetector can be performed without using an extra optical transmission medium. It was.

  The traveling direction of the light beam incident from the light incident portion of the prism 16a is not necessarily the same as the traveling direction of the light beam emitted from the light emitting portion of the prism 16b, and the prism is arranged so that the light receiving portion can be easily arranged. The direction of reflection by 16 can be selected.

  Further, it is not necessary to use the prisms 16a and 16b for both incidence and emission, and the light incident portion and the light emission portion may be separated by using either the incidence or the emission. In this embodiment, the light incident direction and the light emitting direction are substantially the same, but there is an angle of about 180 ° between these directions. Therefore, when the prism 16a is omitted or another optical member is used and the light incident direction with respect to the light emitting direction is set to 90 ° or more and 180 ° or less, the optical fiber 10 is connected when the optical fiber 10 is connected to the light receiving unit. Is desirable because it does not directly hit the light receiving section and connection is easy. That is, the prism has a function of an optical path changing member that bends the optical path of the incident and outgoing light beams. In addition to the reflection of light by the prism, the optical path is changed using other optical members such as refraction and diffraction. It can be bent.

  In this embodiment, the optical block 18 is used to integrate the light incident end 50, the concave mirror 14, the diffraction grating 12, and the light receiving optical waveguide 28 together. Therefore, it is possible to reduce interface reflection that occurs when a lens or the like is used to propagate the light beam and collect the light beam, and the loss of the light beam can be reduced.

  Moreover, it is not necessary to provide an antireflection film or the like for preventing reflection at the interface, and the production becomes easy. In addition, the integrated structure makes it difficult to shift the position between components, and is excellent in environmental changes and long-term stability.

  Hereinafter, further details of each part will be described.

  In the present invention, the diffused light beam 42 emitted from the optical fiber 10 is focused on the chirped diffraction grating 12 and the concave mirror 14 according to the focusing direction.

  That is, the concave mirror 14 was used in the engraving direction (y direction) of the chirped diffraction grating 12, and the chirped diffraction grating 12 focused the light within the xz plane.

  Thus, since the y-direction is collimated by the concave mirror 14 and the chirped diffraction grating 12 is irradiated with the light beam 42, the height φ in the y-direction of the light beam 42 that strikes the chirped diffraction grating 12 can be reduced. The optical block 18 and thus the duplexer 1 could be thinned.

  Thus, since the thickness of the duplexer 1 in the y direction can be reduced, the prism 16 is provided in the optical block 18, or the light receiving optical waveguide 28 and the photodetector array 26 are disposed on the optical block 18. In other words, the duplexer 1 can be thinned and miniaturized.

  Furthermore, since the chirped diffraction grating 12 is used in the present invention, the wavelength separation width is determined by the distance from the chirped diffraction grating 12 to the condensing point.

  On the other hand, in the conventional demultiplexer, for example, the optical demultiplexer disclosed in Patent Document 1, since the wavelength separation width is proportional to the focal length of the concave mirror, an extra distance from the diffraction grating to the concave mirror is required. The vessel becomes larger.

  Therefore, the present duplexer can be reduced in size because the distance from the concave mirror 14 to the condensing point can be shortened as compared with the conventional duplexer.

  The concave mirror 14 makes the incident light beam have a desired parallelism, and a parabolic mirror having a parabolic cross section can be used as an example of the concave mirror 14.

  If the end face of the optical fiber 10 and the incident end face 44 of the light receiving optical waveguide 28 are provided in the vicinity of the focal position of the parabolic mirror, a light beam substantially parallel to the z direction can be obtained.

  When a multi-mode optical fiber is used as the optical fiber 10, the incident end is widened, and perfect parallel light cannot be obtained. Therefore, the desired condensing performance of the chirped diffraction grating 12 and the light receiving optical waveguide 28. It is necessary to determine the shape of the concave mirror 14 so that the optical coupling efficiency can be obtained.

  When a parabolic mirror is used, it is desirable to determine the size of the parabolic mirror so that the necessary light collecting performance can be obtained. The concave mirror 14 only needs to have a desired degree of parallelism, and another aspherical shape may be used in addition to the paraboloid.

  Here, the collimation of the light beam 42 incident from the optical fiber 10 using one concave mirror 14 and the condensing of the light beam 43 diffracted by the chirped diffraction grating 12 are combined.

  The condensing of the incident light and the outgoing light may be realized using separate concave mirrors, for example, the reflecting surface of the prism 16 may be a concave shape. In this case, it is possible to change the focal length by changing the curvature of each concave mirror.

  The reflecting surfaces of the prism 16, the concave mirror 14, and the diffraction grating 12 are coated so as to obtain a desired reflectance. As the coating material, a metal reflective film such as gold, aluminum, silver or the like can be used.

  When a higher reflectance is required, a reflective coating using a dielectric multilayer film may be used. Further, when the light incident angle to the prism 16 or the concave mirror 14 is increased to cause total reflection at the interface, it can be used without any coating.

  Next, the chirped diffraction grating 12 will be described.

  In order to reduce the width of the duplexer 1, that is, to reduce the width of the optical block 18, it is desirable to arrange the light incident position and the condensing position of the chirped diffraction grating 12 close to each other. That is, it is desirable that the center of the chirped diffraction grating 12 is close to a Littrow arrangement that diffracts in the incident direction.

  Further, as a characteristic of the chirped diffraction grating 12, it is desirable that the diffraction efficiency is high in the wavelength range to be used. In addition, when the incident light beam is polarized, it is desirable that the polarization dependency of the diffraction efficiency is small. .

  FIG. 2 shows the relationship between the diffraction efficiency and the lattice constant / wavelength at that time when the diffraction efficiency of TE-polarized light and TM-polarized light are equal in the Littrow arrangement with the blaze angle as a parameter.

  In FIG. 2, when the blaze angle is increased, the grating constant can be reduced, and the wavelength dispersion of the chirped diffraction grating can be increased. Therefore, there is an advantage that the duplexer can be reduced. However, on the other hand, it turns out that diffraction efficiency falls.

  However, the diffraction efficiency is improved specifically between the blaze angles of 21 ° to 34 °. Therefore, if the blaze angle is 21 ° or more and 34 ° or less at the center of the chirped diffraction grating 12, low polarization dependence and high diffraction efficiency and miniaturization of the optical demultiplexer can be achieved.

  At this time, the ratio between the grating constant and the wavelength at the center of the chirped diffraction grating 12 is 0.88 or more and 1.41 or less. The wavelength in this case may be a design wavelength of the chirped diffraction grating 12 or a wavelength included in a wavelength range in which a duplexer is used.

  The focal length of the chirped diffraction grating 12 varies depending on the wavelength, and the focal length is shorter as the wavelength is longer.

  In the light receiving optical waveguide 28, in order to reduce the crosstalk between wavelengths and to separate the wavelengths, the condensing position by the chirped diffraction grating 12 is set in the light receiving optical waveguide 28 within the used wavelength region. There is a need.

  On the other hand, in order to make light incident on the light receiving optical waveguide 28 efficiently, it is necessary to arrange the incident end surface 44 of the light receiving optical waveguide 28 to be at the focal position of the concave mirror 14. Therefore, the condensing position of the chirped diffraction grating 12 for the longest wavelength in the wavelength range to be used needs to be the same as or farther from the focal position of the concave mirror 14.

  That is, it is necessary to change the grating constant so that the condensing position on the chirped diffraction grating 12 is focused on the exit end face of the prism 16b or on the outer side of the exit end face.

  In general, the light loss per unit length generated in the light receiving optical waveguide 28 is larger than the light loss generated in the optical block 18. Therefore, in order to reduce the light loss, the light receiving optical waveguide 28 is shortened. It is desirable to do.

  For this purpose, the position where light is collected by the chirped diffraction grating 12 for the longest wavelength in the wavelength range to be used is substantially equal to the focal position of the concave mirror 14, and the light-receiving optical waveguide 28 is located at this position. It is desirable to arrange so that the incident end face 44 comes.

  When the paraxial focal position and the best image point position at which the spot diameter is minimum are different due to the aberration of the chirped diffraction grating 12, the best image point position of the chirped diffraction grating 12 and the focal position of the concave mirror 14 are different. What is necessary is just to make it substantially equal.

  The grating constant of the chirped diffraction grating 12 was varied as a function of the diffraction grating location so as to have the desired light collection performance. The position of each grating groove can be determined from the incident position and the condensing position of the light beam.

  In general, the lattice constant is determined so that the best light collection performance can be obtained for a specific wavelength (design wavelength).

  As the groove shape of the chirped diffraction grating 12, it is desirable to use a so-called Eschlet type in which the cross-sectional shape of the grating groove is a right triangle so as to obtain high diffraction efficiency.

  In order to increase the diffraction efficiency, it is desirable to change the blaze angle in accordance with the incident / exit angle at each grating position.

  The light beams 42 and 23 propagate through the optical block 18 and have a smaller divergence angle than when propagating through the air. Therefore, the irradiation width w of the light beams 42 and 43 impinging on the chirped diffraction grating 12 is narrowed in the xz plane.

  As a result, the chirped diffraction grating can be made small, the diffraction grating can be easily processed, and the diffraction efficiency of the chirped diffraction grating 12 can be increased.

  Further, since the irradiation range to the chirped diffraction grating 12 is reduced, the aberration generated when the incident wavelength is changed from the design wavelength of the chirped diffraction grating 12 is reduced.

  Therefore, even if the incident wavelength changes from the design wavelength, the change in spot diameter is reduced, the occurrence of crosstalk between wavelengths is suppressed, and the wavelength transmission bandwidth can be widened.

  The chirped diffraction grating 12 may be separately attached to the optical block 18 or may be integrally formed with the optical block 18.

  As the diffraction grating, a diffraction grating having a light condensing property in a uniaxial direction may be used, and not only the planar chirped diffraction grating shown in this embodiment but also a concave diffraction grating formed on a cylindrical surface can be used.

  When a concave diffraction grating is used, the slab waveguide portion 38 does not have to be provided in the light receiving optical waveguide 28, and only the tapered waveguide portion 40 can be provided. Alternatively, the photodetector array 26 and the outgoing optical fiber array can be provided directly on the outgoing face of the prism 16b without providing the light receiving optical waveguide 28.

  The optical block 18 may be configured using a transparent material in the wavelength region to be used, and glass or a polymer material can be used.

  In order to increase the light receiving efficiency, it is desirable to use a material that absorbs less light at the wavelength used, and as the polymer material, PMMA, polycarbonate, amorphous alicyclic polyolefin, polystyrene, or the like can be used.

  The optical block 18 may be formed by processing each part separately and combining parts, or may be integrally formed. For example, when a polymer material is used, the prism 16 and the concave mirror 14 can be integrally formed by injection molding, and further, the chirped diffraction grating 12 can be molded at the same time.

  Here, as shown in FIG. 1A, the optical fiber 10 is inclined and connected to the incident surface of the prism 16a so that the condensing characteristics of the concave mirror 14 are substantially equal between the incident and outgoing light beams. Therefore, the light beam enters and exits the concave mirror 14 substantially symmetrically.

  If the difference between the angles at which the incident and outgoing light beams are incident on the concave mirror 14 is small, the optical fiber 10 can be substantially perpendicular to the incident surface of the prism 16a. In this case, arrangement becomes easy when the duplexer 1 is mounted in the optical module.

  Alternatively, the incident surface of the prism 16a may be tilted so that the light beam is substantially perpendicular to the incident surface of the prism 16a.

  When the chirped diffraction grating 12 is fixed to the optical block 18 as in this embodiment, it is considered that a change in refractive index, expansion and contraction, etc. occur due to an environmental change such as a temperature change and affect the characteristic variation.

  Therefore, assuming that the refractive index of the optical block 18 is n and the lattice constant of the chirped diffraction grating 12 is d, if the fluctuation of the product nd is small, the characteristic fluctuation of the diffraction grating is small. In general, when the temperature rises, the diffraction grating thermally expands and the grating constant d increases, but the refractive index n of the optical material decreases.

  Therefore, by fixing the chirped diffraction grating 12 to the optical block 18, it is possible to suppress changes in characteristics due to temperature changes.

  Next, the light receiving optical waveguide 28 will be described.

  FIG. 3 shows a top view of the light receiving optical waveguide 28. The light receiving optical waveguide 28 includes a slab waveguide portion 38 and a tapered waveguide portion 40.

  In this embodiment, since the chirped diffraction grating 12 is used, the focal point moves in the lateral direction (x direction) and the focal length changes (moves in the z direction) depending on the wavelength of the optical signal.

  In view of this, the slab waveguide portion 38 corresponds to the focal length change (z direction) due to the wavelength variation, and the tapered waveguide portion 40 corresponds to the converging position movement in the lateral direction (x direction) due to the diffraction angle change. .

  The optical signal diffracted by the chirped diffraction grating 12 is condensed by the concave mirror 14 onto the incident end 44 of the slab waveguide section 38 and enters the light receiving optical waveguide 28. Therefore, it is necessary to determine the thickness of the light receiving optical waveguide 28 in consideration of both the optical coupling by the concave mirror 14 and the optical coupling with the photodetector array 26.

  The shape of the slab waveguide portion 38 was determined so that the light beam collected by the chirped diffraction grating 12 was focused on the junction 46 between the slab waveguide portion 38 and the tapered waveguide portion 40.

  That is, since the focal length of the chirped diffraction grating 12 becomes longer as the wavelength is shorter, the distance from the incident end 44 to the junction 46 is increased as the wavelength is shorter.

  The tapered waveguide portion 40 has a tapered shape in which the core width decreases along the light traveling direction from the joint 46 side. Even if the light condensing position fluctuates on the joint 46 due to wavelength variation, a predetermined light is obtained. The detector array 26 can be coupled.

  The slab waveguide portion 38 and the tapered waveguide portion 40 are collectively formed on the same optical waveguide substrate 34, and the thickness of the core can be made constant.

  In the present embodiment, since the tapered waveguide section 40 is used, the light beam can be efficiently coupled to the photodetector array 26 having a small light receiving diameter, and the light receiving diameter can be reduced to reduce the size of the photodetector array 26. Since the photodetectors can be separated from each other, electrical crosstalk can be reduced and an optical signal modulated at high speed can be received.

  In the taper waveguide section 40, the light incident angle increases every time the light is reflected by the taper section, so that light loss is likely to occur. In order to suppress this optical loss, it is desirable that the numerical aperture of the light receiving optical waveguide 28, particularly the numerical aperture of the side surface of the tapered waveguide portion 40, be large. Therefore, it is desirable not to provide a clad layer on the tapered side surface but to be in direct contact with air.

  Further, as shown in FIG. 1B, it can be used without forming a clad on the lower side of the core 30 opposite to the optical waveguide substrate 34. As described above, when the clad can be formed only on the core 30 without forming the clad on the tapered side surface, it is desirable to form the clad 32 also on the core 30.

  4 is a cross-sectional view of the light-receiving optical waveguide 28 shown in FIGS. 1 and 3. FIG. 4A is a cross-sectional view seen from the optical waveguide emitting end face 45 side of FIG. 3, and FIG. FIG. 4 is a side sectional view of the vicinity of the optical waveguide incident surface 44 of FIG. 3.

  In the light receiving optical waveguide 28, a waveguide clad 32 is provided on a waveguide substrate 34, and a waveguide core 30 is formed thereon. In this case, no clad is provided on the upper surface of the waveguide core 30 (on the side opposite to the waveguide substrate 34). For this reason, it is desirable to suppress adhesion of dust or the like on the waveguide core 30 of the light receiving optical waveguide 28.

  Therefore, the light receiving optical waveguide 28 is installed on the base 20 having the cavity 48 provided on the optical block 18 with the waveguide core 30 facing the cavity 48.

  In this way, by providing the base 20 having the cavity 48 and covering and protecting the waveguide core 30, adhesion of dust and the like can be suppressed, and long-term stability of the optical waveguide can be ensured without providing a cladding. .

  In addition, the optical waveguide core can be positioned in the height direction (y direction) by using the table 20 as a reference plane so that the table 20 and the clad 32 are in contact with each other.

  In order to reduce light loss due to reflection, it is desirable to reduce reflection between the prism 16b and the optical waveguide entrance end 44 surface by using an optical adhesive 36 or a refractive index matching agent.

  Even when the upper cladding layer is not provided, the optical adhesive 36 is formed on the waveguide core 30 of the slab waveguide section 38 by taking a refractive index matching using a refractive index sufficiently smaller than the refractive index of the core. Alternatively, even if the refractive index matching agent protrudes, light does not leak from the core, and the light receiving optical waveguide 28 can be connected without causing optical loss without providing an upper cladding.

  It is desirable that the photodetector array 26 is adjusted in position so that the beam from the light receiving optical waveguide portion 28 is efficiently coupled to the photodetector, and is bonded and fixed to the emission end 45 of the light receiving optical waveguide portion 28. In order to improve the reliability of the photodetector, when the photodetector array 26 is packaged, the light beam may be directly incident on the photodetector array 26.

  As the light receiving optical waveguide 28 of this embodiment, for example, as disclosed in Patent Documents 3 and 4, a polymer optical waveguide created by light exposure can be used. Alternatively, it can be formed by etching such as reactive ion etching by a photolithography method, and the waveguide material can also be manufactured using an inorganic material such as glass.

  Here, as shown in FIG. 1, the case where the light receiving optical waveguide 28 is inclined with respect to the emission surface of the prism 16b is shown. In this case, it is desirable to make the light receiving optical waveguide 28 easier to create if the incident end face and the outgoing end face of the light receiving optical waveguide 28 are substantially parallel to each other.

  FIG. 5 shows an embodiment of a duplexer provided with a preamplifier 22 as an amplifier circuit that converts a current signal output from the photodetector array 26 into a voltage signal and amplifies the voltage signal.

  FIG. 5A is a side view of the duplexer, and FIG. 5B is a top view of the duplexer. When receiving a high-speed optical signal, it is desirable to arrange the preamplifier 22 as close to the photodetector array 26 as possible in order to suppress noise contamination.

  Here, the circuit board 24 for the preamplifier 22 is disposed on the duplexer 1 so that the preamplifier 22 is disposed in the vicinity of the photodetector array 26. Therefore, even when a high-speed optical signal is received, the deterioration of the S / N ratio due to the mixing of noise is suppressed. In addition, although it has shown about the case where the optical waveguide board | substrate 34 and the circuit board 24 are used as another board | substrate, the optical waveguide board | substrate 34 and the circuit board 24 can also be used.

  Therefore, when an optical waveguide is formed on the circuit board 24, the optical waveguide can be formed thereon by providing a flattening layer that flattens the unevenness of the circuit board 24.

  Therefore, for example, a printed wiring is formed on one side of the circuit board 24 to mount an electrical component, and a light receiving optical waveguide 28 can be formed on a reverse surface after forming a planarization layer. This planarizing layer may be used as the cladding layer of the light receiving optical waveguide 28, or a cladding layer may be further provided on the planarizing layer.

  In this embodiment, since the optical demultiplexer can be thinned, and the emission direction of the demultiplexed light and the incident direction of the light are aligned and arranged at positions facing each other across the prism, In addition to the light receiving optical waveguide 28, the circuit board 24 can be disposed. The circuit board 24 can be supported using the prism 16b.

  In this embodiment, the incident optical fiber 10 is not particularly limited, but the shape of the concave mirror 14 and the diffraction grating 12 are set so that desired characteristics can be obtained as the core diameter and numerical aperture of the optical fiber increase. The core thickness and core shape of the optical waveguide 28 for light reception need to be determined and determined. Therefore, these conditions are particularly severe when a multimode optical fiber is used.

  In general, among optical fibers used for high-speed optical communication, a GI type multimode optical fiber having a core diameter of 62.5 μm and a numerical aperture of 0.275 is given as one having a large core diameter and numerical aperture. . If this optical fiber can be accommodated, it is possible to receive light without degrading characteristics of an optical fiber having a smaller core diameter and numerical aperture.

  When the optical fiber 10 having a large numerical aperture such as a multimode optical fiber is used, there is a problem that the light irradiation width to the chirped diffraction grating 12 is increased and the aberration caused by the chirped diffraction grating 12 is increased.

  When propagating through the optical member 18 as in this embodiment, the light beam divergence angle is reduced by the refractive index of the optical member 18, and the light irradiation width w to the chirped diffraction grating 12 is reduced.

  The third-order coma generated by the chirped diffraction grating is approximately proportional to the cube of the light irradiation width w. Therefore, it is propagated through the optical member and irradiated to the chirped diffraction grating by the chirped diffraction grating. There is a great effect in reducing the generated aberration.

  Propagating through the optical member in this way has a great effect of reducing aberrations when using an optical fiber having a large numerical aperture, and is therefore effective when using a multimode optical fiber.

  Another embodiment of the present invention will be described with reference to FIG.

  6A and 6B are diagrams for explaining an optical demultiplexer according to the present invention. FIG. 6A is a top view of the optical demultiplexer, and FIG. 6B is a cross-sectional view taken along line AA ′ of the optical demultiplexer. It is.

  In this embodiment, a gap 52 is provided between the concave mirror 14 and the chirped diffraction grating 12 so that the light beams 42 and 43 pass through the air. Other configurations are the same as those in FIG. 1, and the same reference numerals are used.

  By providing the gap 52, the optical block 18 can be formed using an optical material that absorbs light to some extent. In the infrared wavelength region, generally, the light absorption of the polymer material increases, and the optical block 18 causes light propagation loss. However, by providing the gap portion 52, even when the optical block 18 is formed using a polymer material, optical loss can be reduced particularly when an optical signal having an infrared wavelength is received.

  As described above, when the polymer material is used, the optical block 18 can be easily formed by injection shaping, and the optical block 18 can be formed by integrating the prism 16 and the concave mirror 14.

  Furthermore, the chirped diffraction grating 12 can also be molded simultaneously. Since the light beam propagates in the air, the characteristic fluctuation due to the refractive index change of the optical block 18 is reduced.

  As described above, the case where the optical fiber is used in the duplexer has been described. However, it can also be used as an optical multiplexer by making light incident from the photodetector side. Moreover, although the case where the optical fiber is used as the optical transmission medium for light incidence is shown, naturally it can replace with an optical waveguide.

  Examples of the present invention will be described below.

  The embodiment shown in FIG. 1 was used as an embodiment of the optical demultiplexer. In this embodiment, a wavelength multiplexed signal corresponding to the 10GBASE-LX4 standard is demultiplexed.

  In other words, four wavelengths at intervals of 24.5 nm of center wavelengths 1275.7, 1300.2, 1324.7, and 1349.2 nm are separated, and the incident signal has a wavelength shift of ± 6.7 nm with respect to each center wavelength. Permissible. A duplexer was created to meet this specification.

  The distance from the light incident part 50 to the center of the chirped diffraction grating 12 was 12 mm, and the incident angle was 30 °. At this time, the diffraction angle in the used wavelength range is 20.7 to 24.3 °, and each central wavelength is condensed at a position about 250 μm apart in the x direction.

  In addition, the blaze angle at the center of the chirped diffraction grating 12 is set to 32 ° so that both the size reduction of the duplexer and the high diffraction efficiency and low polarization dependency can be achieved.

  The design wavelength of the chirped diffraction grating 12 was 1312 nm, which is the center wavelength of the wavelength range to be used, and the ratio between the grating constant and the design wavelength at the center of the chirped diffraction grating 12 was 1.18.

  The optical block 18 was made using glass. In this embodiment, the concave mirror 14, the prism 16, and the chirped diffraction grating 12 are bonded together to form a monolithic duplexer.

  The optical fiber 10 can be adapted to a refractive index profile (GI) type multimode optical fiber (numerical aperture 0.275) having a core diameter of 62.5 μm.

  The divergence angle in the air of the light beam emitted from the optical fiber 10 is ± 16 °, but is reduced to ± 10.5 ° in the optical block 18 due to the refractive index (1.51) of the optical block 18. Is done.

  Therefore, the light irradiation width w to the chirped diffraction grating 12 is reduced from 8.2 mm when propagating through the air to 5.2 mm by using the optical block 18.

  Since the aberration caused by the chirped diffraction grating 12 is approximately proportional to the cube of the irradiation width w, it is strongly influenced by the aberration particularly when an optical fiber having a large numerical aperture is used. That is, the reduction of the irradiation width w is effective in reducing aberration particularly when a multimode optical fiber having a large numerical aperture is used.

  Further, since the aberration increases when the wavelength variation from the design wavelength is large, it is effective when applied to CDWM (Coarse Wavelength Division Multiplexing) having a wide wavelength width as in this embodiment.

  In the present embodiment, the position where the longest wavelength in the wavelength range to be used, that is, the light beam having a wavelength of 1355.9 nm is collected by the chirped diffraction grating 12 is made equal to the focal position of the concave mirror 14. The incident end face 44 of the light receiving optical waveguide 28 is disposed at this position. This condensing position is set to the best image point position where the spot diameter is minimized in consideration of the aberration generated in the chirped diffraction grating 12.

  Since this duplexer optical system has a lateral magnification of about 1 time, the core thickness of the light receiving optical waveguide 28 is the same as the core diameter of the optical fiber 10 for efficient optical coupling to the light receiving optical waveguide 28. It is desirable to make it thicker than the degree or core diameter.

  On the other hand, in order to detect a high-speed modulated optical signal, it is desirable that the light receiving diameter of the photodetector is small, and the core thickness of the light receiving optical waveguide 28 can be reduced in accordance with the light receiving diameter of the photodetector. desirable. In this example, the core thickness was set to 65 μm so as to substantially match the core diameter of the optical fiber.

In FIG. 7, when a GI type multimode optical fiber having a core diameter of 62.5 μm is used as the optical fiber 10 and the core thickness of the light receiving optical waveguide 28 is 65 μm, the radius of curvature R, the optical coupling loss, and the beam height of the concave mirror 14 are obtained. The relationship of φ is shown. Here, when the radius of curvature is R, the parabolic shape is expressed as z = y ² / 2R. This radius of curvature R indicates the radius of curvature at the center of the paraboloid.

  From FIG. 7, the coupling loss decreases as the radius of curvature R of the concave mirror 14 is increased. If the radius of curvature R is 3 mm or more, the loss can be almost zero. If the radius of curvature R is 2 mm or more, the loss is practically small. However, when the radius of curvature R is increased, the beam height φ increases and the optical block 18 needs to be thickened. Therefore, since the optical demultiplexer becomes large, it is desirable that the radius of curvature R is small. Therefore, in this example, it was set to 4 mm.

  In the chirped diffraction grating 12 of this example, the diffraction grating is divided into regions, a constant blaze angle is set in the region, and the blaze angle is optimized for each region so that the diffraction efficiency is increased. Such a diffraction grating was processed using a ruling engine while changing the grating constant at a constant blaze angle for each region. For the optical demultiplexer 1, a replica made using this diffraction grating as a master was used.

  In the present embodiment, an optical fiber for optical signal transmission is used as it is for the optical fiber 10, and the optical fiber 10 is inserted and removed without being fixed to the duplexer 1. In that case, an insertion guide or the like may be used so that the optical fiber 10 fixed to the optical connector is abutted at a predetermined position even when the optical fiber 10 is inserted or removed. In addition, an antireflection film was provided on the incident surface to reduce light loss due to reflection.

  As described above, since desired characteristics can be obtained according to the multimode optical fiber, even when an optical fiber having a numerical aperture or a core diameter smaller than that of the predetermined multimode optical fiber is connected as the optical fiber 10, Characteristics equivalent to or better than when a predetermined multimode optical fiber is connected can be obtained. Therefore, the optical fiber 10 to be connected is not limited to a predetermined multimode optical fiber, and an optical fiber having a small numerical aperture or core diameter may be connected.

  In this embodiment, a single mode optical fiber, for example, a multimode optical fiber having a core diameter of 50 μm, or the like can be connected instead of the 62.5 μm GI multimode optical fiber. The optical fiber 10 may be bonded to the prism 16a.

  When the optical fiber 10 is fixed, the transmission optical fiber may be abutted against the other end of the optical fiber 10 and light may be incident on the duplexer. Even in this case, the numerical aperture and diameter of the transmission optical fiber may be equal to or smaller than those of the optical fiber 10.

  Therefore, the same GI type multimode optical fiber as the optical fiber 10 may be connected to the optical fiber 10, and a single mode optical fiber (SMF) having a small fiber diameter / numerical aperture or a multimode optical fiber having a core diameter of 50 μm may be used. It can also be connected.

  Further, the specification can be determined so as to correspond to another GI type multimode optical fiber instead of the GI type multimode optical fiber having a core diameter of 62.5 μm. Since the core diameter and numerical aperture of GI type multimode optical fiber are generally 50 μm or more and 0.2 or more, respectively, it is desirable.

  Other than the 62.5 μm multimode optical fiber, a 50 μm multimode optical fiber, a step index (SI) type as well as a GI type, and a plastic optical fiber having a larger core diameter may be used.

  As for the number of multiplexed wavelength signals and the wavelength interval, it is only necessary to obtain desired characteristics according to predetermined specifications, and it is possible to comply with ITU-T694.2 with a wavelength interval of 20 nm. The present invention is not limited to CWDM as in this embodiment, and application to DWDM is also possible.

  The embodiment shown in FIG. 6 was used as an example of the optical demultiplexer according to the present invention.

  In this embodiment, the optical block 18 is injection molded using polycarbonate. At the same time, the chirped diffraction grating 12 was also injection molded.

  The chirped diffraction grating 12 is integrated with the optical block 18 via a support portion 54. Since the light beams 42 and 43 pass through the gap 52 having a refractive index different from that of the optical block 18, the grating constant of the chirped diffraction grating 12 is modulated so that a desired light collecting performance can be obtained.

  FIG. 8 is a block diagram showing an embodiment of the wavelength division multiplexing optical transmission module according to the present invention. The transmission optical fibers 74 a and 74 b are connected to the optical transmission module 80 by a connector 96.

  The optical fiber 74 b is further abutted with the single mode optical fiber 11. The wavelength multiplexed signal transmitted through the receiving transmission optical fiber 74a is directly incident on the demultiplexer 1, separated for each wavelength, and detected by the photodetector array 26. This detection signal is amplified by the pudding amplifier 22 and further amplified by the receiving circuit 86 and shaped in waveform. Then, the parallel / serial conversion circuit 90 converts the separated parallel signal into a serial signal and outputs it.

  In the case of transmission, the input signal is separated by the serial / parallel conversion circuit 92, and each light source of the laser diode array 94 is driven for each signal by the transmission circuit 88 to obtain an optical signal having a different wavelength.

  Each optical signal is multiplexed by a multiplexer 84 composed of a single mode optical coupler and output to the single mode optical fiber 11. The single mode optical fiber 11 is coupled to the transmission optical fiber 74b for transmission and transmitted.

  Since the single mode optical fiber 11 is used to couple with the transmission optical fiber 74b, either the multimode optical fiber or the single mode optical fiber can be used for the transmission optical fibers 74a and 74b.

  In this embodiment, since a GI type multimode fiber having a core diameter of 62.5 μm is used for the optical fiber 10, a single mode optical fiber having a core diameter of 50 μm and 62.5 μm is used as the transmission optical fibers 74 a and 74 b. A mode optical fiber or the like can be used.

  In the present embodiment, four wavelengths at intervals of 24.5 nm of the center wavelengths 1275.7, 1300.2, 1324.7, and 1349.2 nm that have been multiplexed and transmitted in accordance with the 10GBASE-LX4 standard are separated. The configuration.

  In this embodiment, the multiplexer 84 and the transmission optical fiber 74b are coupled by the single mode optical fiber 11. However, when only the multimode optical fiber is used for the transmission optical fiber 74b, the single mode optical fiber is used. In this case, a multimode optical waveguide may be used for the multiplexer 84.

  By using the multi-mode optical waveguide, the multiplexer 84 and the laser diode array 94 can be easily adjusted. Further, an optical signal may be directly input from the multiplexer 84 to the transmission optical fiber 74b without using the single mode optical fiber 11.

  In the present embodiment, the wavelength multiplexing transmission module having both transmission and reception functions is shown, but the effect of the present invention can also be obtained as a wavelength multiplexing optical reception module having only a receiving section.

  This embodiment is suitable for receiving an optical signal transmitted by a multimode optical fiber, and is suitable for CWDM as described above. However, application to DWDM (Dense WDM) is not limited. Further, although the case of the wavelength multiplexing number 4 has been described, the multiplexing number is not limited and may be appropriately selected according to the system to be used.

  As described above, since the optical signal input to the optical demultiplexer used in the present invention does not necessarily have to be modulated and does not need to include a plurality of wavelengths at the same time, the light intensity is simply detected by separating the wavelengths. Alternatively, the present invention can be applied to a spectrometer that separates and extracts an optical signal.

Top view and side view of duplexer according to the present invention Relationship diagram between blaze angle, diffraction efficiency and grating constant / wavelength of chirped diffraction grating in FIG. 1 is a top view of the light receiving optical waveguide 28 in FIG. Sectional view and side sectional view of the light receiving optical waveguide 28 in FIGS. The top view and side view which provided the preamplifier 22 in the splitter which concerns on this invention Top and side views of another duplexer according to the present invention Relationship diagram between radius of curvature of concave mirror 14 and light receiving optical waveguide and beam height in the present invention Configuration diagram of wavelength division multiplexing optical transmission module

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Splitter, 10 ... Optical fiber, 11 ... Single mode optical fiber, 12 ... Chirped diffraction grating, 14 ... Concave mirror, 16 ... Prism (optical path changing member), 16a, 16b ... 1st, 2nd prism (1st (1) and (2) optical path conversion member), 18 ... optical block, 20 ... stand, 22 ... preamplifier, 24 ... circuit board, 26 ... photodetector array, 28 ... optical waveguide for light reception, 30 ... waveguide core, 32 ... Waveguide cladding 34: Waveguide substrate 36: Adhesive 38: Slab waveguide part 40 ... Tapered waveguide part 42, 43 ... Light beam 44 ... Optical waveguide entrance end face 45 ... Optical waveguide exit end face 46 ... Junction part, 48 ... Cavity part, 50 ... Light incident part, 52 ... Gap part, 54 ... Support part, 74a, 74b ... Transmission optical fiber, 80 ... Optical transmission device, 84 ... Multiplexer, 86 ... Reception Circuit, 88 ... Transmission circuit, 90 Parallel / serial conversion circuit, 92 ... a serial / parallel conversion circuit, 94 ... laser diode array, 96 ... optical connector

Claims (13)

A light incident part on which a wavelength-multiplexed light beam is incident, an optical path for transmitting the light beam incident on the light incident part, and a diffraction that irradiates the light beam transmitted on the optical path and separates an optical signal for each wavelength. In an optical demultiplexer having a grating and a light emitting part for extracting an optical signal separated by the diffraction grating,
A first optical path conversion member that bends the optical path of the light beam incident from the light incident portion;
A concave mirror that condenses the light beam from the first optical path changing member in a uniaxial direction so as to reduce the divergence angle in the groove direction of the diffraction grating;
The diffraction grating condenses the light beam whose uniaxial divergence angle is reduced by a concave mirror in a uniaxial direction different from the condensing axis of the concave mirror,
A second optical path conversion member that bends the optical path of the optical signal separated for each wavelength by the diffraction grating;
The optical demultiplexer, wherein the first optical path changing member and the second optical path changing member are arranged between the light incident part and the light emitting part. A light incident part on which a wavelength-multiplexed light beam is incident, an optical path for transmitting the light beam incident on the light incident part, and a diffraction that irradiates the light beam transmitted on the optical path and separates an optical signal for each wavelength. In an optical demultiplexer having a grating and a light emitting part for extracting an optical signal separated by the diffraction grating,
An optical path conversion member that bends the optical path of the light beam in the optical path;
A concave mirror for condensing light in a uniaxial direction so as to reduce a spreading angle in the groove direction of the diffraction grating;
The diffraction grating condenses light in a uniaxial direction different from the condensing axis of the concave mirror, the light beam whose uniaxial divergence angle is reduced by the concave mirror,
The optical path changing member is formed such that an angle of a traveling direction of the light beam incident from the light incident portion with respect to a traveling direction of the light beam emitted from the light emitting portion is 90 ° or more and 180 ° or less. An optical demultiplexer characterized by The optical demultiplexer according to claim 1 or 2,
The optical path is formed of a transparent optical member;
An optical demultiplexer characterized in that the light beam propagates in an optical member from a light incident part to a light emission part The optical demultiplexer according to claim 1 or 2,
A part of the optical path is formed of a transparent optical member,
An optical demultiplexer characterized in that the light beam propagates in air from a light incident part to a light emission part The optical demultiplexer according to claim 1 or 2,
The optical demultiplexer characterized in that the diffraction grating is a chirp type formed on a substantially plane. The optical demultiplexer according to claim 1 or 2,
An optical demultiplexer characterized in that a multi-mode optical transmission medium is connected to the light incident portion and a light beam is incident thereon. The optical demultiplexer according to claim 1 or 2,
The blaze angle at the center of the diffraction grating is 21 ° or more and 34 ° or less, and the ratio between the grating constant of the diffraction grating and the wavelength used is 0.88 or more and 1.41 or less. vessel The optical demultiplexer according to claim 1 or 2,
An optical demultiplexer having an optical waveguide connected to the light emitting portion The optical demultiplexer according to claim 8, wherein
The best image point position where the light beam having the longest wavelength in the wavelength range incident as the light beam is collected by the diffraction grating and the focal position where the light beam is collected by the concave mirror are substantially equal, and the incident end face of the optical waveguide. Optical demultiplexer characterized by coming up The optical demultiplexer according to claim 8, wherein
An optical demultiplexer characterized in that the optical waveguide is disposed substantially parallel to a light beam entering and exiting the diffraction grating The optical demultiplexer according to claim 8, wherein
A photodetector for receiving a light beam from the optical waveguide;
An amplification circuit for amplifying an electric signal from the photodetector,
An optical demultiplexer characterized in that the amplifier circuit is provided on a substrate on which an optical waveguide is formed or on a circuit substrate disposed substantially parallel to the optical waveguide. In a wavelength multiplexing optical receiver module having a junction with an optical fiber for signal transmission, an optical demultiplexer, a photodetector array, and a receiving circuit that amplifies a signal from the photodetector array and shapes the waveform,
12. The wavelength division multiplexing characterized in that any one of the optical demultiplexers according to claim 1 is used as the optical demultiplexer, and the junction and the optical demultiplexer are connected by a multimode optical transmission medium. Optical receiver module Driving the optical fiber for signal transmission, the optical demultiplexer, the photodetector array, the receiving circuit for amplifying the signal from the photodetector array and shaping the waveform, the light source array, and the light source array In a wavelength division multiplexing optical transmission module having a transmission circuit and an optical multiplexer for multiplexing optical signals from a light source array,
The optical demultiplexer according to any one of claims 1 to 11, wherein the junction and the optical demultiplexer are connected by a multimode optical transmission medium, and the junction and the optical multiplexer are used. Wavelength-multiplexed optical transmission module, characterized by being connected with a single-mode optical transmission medium

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