JP4842915B2 - Optical channel monitor and wavelength selective optical switch - Google Patents

Description

  The present invention relates to an optical channel monitor and a wavelength selective optical switch including the optical channel monitor.

  In recent years, in the field of optical communication, it is possible to perform large-capacity optical transmission using a single optical fiber by WDM (Wavelength Division Multiplexing) technology, in which one optical signal is associated with one wavelength and wavelength-division multiplexed. It has been realized. With the development of such optical communication technology, an optical switch that switches a path without converting an optical signal into an electric signal or the like has attracted attention. In particular, a wavelength selective optical switch (for example, see Patent Document 1) that can select an arbitrary wavelength from several tens of wavelengths and output the selected wavelength to any one of a plurality of output fibers has been proposed. An example of this wavelength selective optical switch (WSS: Wavelength Selective Switch) is shown in FIG.

  The wavelength selective optical switch shown in FIG. 18 includes a fiber array 110, a microlens array 120, a condenser lens 130, a 4f optical system 140, and a MEMS mirror array chip 150, which are in this order. 1 (hereinafter referred to as “Z-axis direction”).

  The fiber array 110 has a configuration in which a plurality of optical fibers (seven in the case of FIG. 18) are juxtaposed in the Y-axis direction orthogonal to the Z-axis in a state where the optical axis is along the Z-axis. In FIG. 18, one input port 111 and six output ports 112 are provided.

  The microlens array 120 includes a plurality of microlenses arranged in parallel along the Y direction. Such a microlens array 120 includes optical fibers of the fiber array 110 corresponding to the microlenses on the output side of the input port 111 and the input side of the output port 112, that is, on the positive side in the Z direction of the fiber array 110. It arrange | positions so that it may oppose.

  The 4f optical system 140 includes a first lens 141 and a second lens 142 each having a focal length f, and a transmissive diffraction grating 143. The first lens 141, the diffraction grating 143, and the second lens 142 are arranged in this order. It is disposed on the positive side in the Z direction from the condenser lens 130. The first lens 141 is disposed at a position separated from the condenser lens 130 by the sum of the focal length of the condenser lens 130 and the focal length f of the first lens 141. The diffraction grating 143 is disposed at a position separated from the first lens 141 by a focal length f. The second lens 142 is disposed at a position separated from the diffraction grating 143 by the focal length f. Here, the plane constituted by the X axis and the X axis at the focal point of the first lens 141 on the condenser lens 130 side and the Y axis perpendicular to the Z axis is the first focal plane, and the MEMS mirror array chip 150 of the second lens 142. A plane composed of the X axis and the Y axis at the focal point on the side is referred to as a second focal plane.

  As shown in FIG. 19, the MEMS mirror array chip 150 includes a plurality of MEMS mirror elements 152 each having a mirror 152a on a base 151 that is substantially rectangular in plan view, and a straight line passing through the center of the mirror 152a is the longitudinal direction of the base 151. That is, it has a configuration arranged along the X-axis direction. Such a MEMS mirror array chip 150 is disposed on the second focal plane with the main surface of the mirror 152a of the MEMS mirror element 152 facing the 4f optical system 140. The mirror 152a of the MEMS mirror element 152 is supported so as to be rotatable with respect to the base 151 in two axial directions: a wavelength separation axis (X axis) and a Y axis perpendicular to the X axis. Accordingly, the output port is selected by rotating the mirror 152a around the X axis (reference numeral α). Further, the attenuation level is controlled by rotating the mirror 152a around the Y-axis (symbol β).

  In such a wavelength selective optical switch, for example, when WDM signal light that is wavelength-separated by 40 waves (channels) at a wavelength channel interval of 100 GHz is input from the input port 111, the WDM signal light is converted into the microlens array 120, The light enters the diffraction grating 143 via the condensing lens 130 and the first lens 141, and is demultiplexed into 40 waves by the diffraction grating 143. Each of the demultiplexed channels is aligned on the X axis of the second focal plane. To form a beam waist. At this beam waist position, a MEMS mirror array chip 150 in which MEMS mirror elements 152 are arranged at an appropriate pitch corresponding to each channel is disposed. As a result, when the MEMS mirror element 152 is rotated by a predetermined angle around the X axis, the channel incident on the MEMS mirror element 152 is reflected in a direction corresponding to the predetermined angle, and the 4f optical system 140, the condensing light is collected. The light enters the predetermined optical fiber of the fiber array 1 through the lens 130 and the microlens array 120 and is output from the predetermined output port 112. In this way, by selectively rotating the MEMS mirror element 152 around the X axis, it is possible to selectively switch the output port for each channel, so-called switching.

  When configuring a reconfigurable optical add / drop module (ROADM) using a wavelength selective optical switch as described above, light for monitoring the light quantity of each wavelength channel at the time of output An external monitor called an channel monitor (OCM: Optical Channel Monitor) is indispensable.

  For example, in the case where the optical multiplexing / demultiplexing module 200 is configured by using an Add type wavelength selective optical switch 210 and an optical channel monitor 220 as shown in FIG. 20, the optical channel monitor 220 usually has an AWG (Arrayed Waveguide Grating) or the like. Are configured as a module including a demultiplexer (Demux) 221 and a PD array 222 having a plurality of PDs (photo diodes). Here, light tapped at an appropriate ratio from the output port of the wavelength selective optical switch 210 is input to the demultiplexer 221 as input light, and the light intensity of each wavelength (channel) is measured by the PD array 222. Based on this measurement value, the control circuit 230 calculates the tilt angle of each mirror of the wavelength selective optical switch 210, and the MEMS drive circuit 240 controls each mirror so that the optimum tilt angle is obtained.

  Further, when the optical multiplexing / demultiplexing module 300 is configured using the drop-type wavelength selective optical switch 310 and the optical channel monitor 320 as shown in FIG. 21, the optical channel monitor 320 is a demultiplexer composed of AWG or the like. The module is composed of a PD array 322 having a plurality of PDs 321 and a plurality of PDs. Here, light tapped at an appropriate ratio from each output port of the wavelength selective optical switch 320 is input to the demultiplexer 321 as input light, and the light intensity of each wavelength (channel) is measured by the PD array 322. Based on this measurement value, the control circuit 330 calculates the tilt angle of each mirror of the wavelength selective optical switch 310 and controls each mirror by the MEMS drive circuit 340 so that the optimum tilt angle is obtained.

JP 2007-140168 A

  However, when configuring an optical multiplexing / demultiplexing module or an optical multiplexing / demultiplexing module subsystem using an optical channel monitor as described above, the size of the optical channel monitor itself is increased and the cost is increased and the size is reduced. It was difficult to realize cost reduction.

  Further, in the case of the ADD type wavelength selective optical switch as shown in FIG. 20, when the optical channel monitor 220 is connected with a tap rate of 20%, for example, an excess loss of about 1 dB occurs, and it is difficult to reduce the loss. Met.

  Further, in the case of a drop-type wavelength selective optical switch as shown in FIG. 21, an optical channel monitor must be connected to each of a plurality of output ports, so that further miniaturization and cost reduction can be realized. It was difficult.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to realize downsizing and cost reduction in an optical channel monitor.

In order to solve the above-described problems, an optical channel monitor according to the present invention includes a first lens disposed on the optical axis of incident light and the incident light incident side of the first lens opposite to the first lens. A transmissive diffraction grating disposed obliquely with respect to the optical axis of the incident light on the side focal point and having a reflecting surface on at least a part of the surface opposite to the first lens, and diffracted by the diffraction grating A second lens disposed on the optical axis of the diffracted light of the incident light and having one focal plane located on the diffraction grating; and the other of the second lenses on the optical axis of the diffracted light A deflecting element that is disposed on the focal plane of the light source and reflects the diffracted light to the diffraction grating, and the diffracted light reflected by the deflecting element is on the optical axis of the reflected light reflected by the reflecting surface of the diffraction grating, and A third lens arranged so that one focal plane is positioned on the diffraction grating; On the axis, and characterized by comprising a third lens of the other light receiving elements arranged in the focal plane side.

  In the optical channel monitor, on the optical axis of the diffracted light diffracted by the second diffraction grating disposed on the optical axis of the incident light reflected by the reflecting surface of the diffraction grating, In addition, a third lens arranged so that the second diffraction grating is located on one focal plane, and a second light receiving element arranged on the other focal plane side of the third lens are further provided. You may do it.

In addition, another optical channel monitor according to the present invention includes a first lens disposed on the optical axis of the incident light and an incident light on a focal point opposite to the incident light incident side of the first lens. A transmission type diffraction grating which is disposed obliquely with respect to the optical axis and has a reflecting surface on at least a part of the surface opposite to the first lens, and light of diffracted light of incident light diffracted by the diffraction grating A second lens disposed on the axis and with one focal plane positioned on the diffraction grating, and disposed on the optical axis of the diffracted light and on the other focal plane of the second lens; A deflecting element that reflects diffracted light and guides it to the diffraction grating, a reflecting mirror disposed on the optical axis of the reflected light reflected by the reflecting surface of the diffraction grating, and the reflecting mirror And a light receiving element arranged on the optical axis of the reflected light reflected by the To. Here, the reflection mirror may be disposed obliquely with respect to the optical axis direction of the reflected light. The reflection mirror may be composed of a concave mirror.

In the optical channel monitor, the first diffraction grating is composed of arranged diffraction grating such that the Littrow arrangement of about 45 degrees with respect to primary or -1 order diffracted light is reflected by the deflecting element The diffracted light may be incident on the diffraction grating at an angle of approximately 45 degrees.

  In the optical channel monitor, the deflecting element may be composed of a plurality of MEMS mirror elements arranged one-dimensionally.

In the above optical channel monitor, the diffraction grating has a grating portion in which a large number of slits are arranged in parallel to each other, and the reflection surface is formed in a band shape in the longitudinal direction of the slit at the end of the diffraction grating. It may be. Further, the reflecting surface is the diffractive grating of a generally rectangular plan view, both ends of the vertical end with respect to the longitudinal direction of the slit, or formed at a substantially central portion of the end parallel to the longitudinal direction of the slit You may make it do.

  In addition, a wavelength selective optical switch according to the present invention includes any one of the above optical channel monitors and an input / output optical system including at least one input port and at least one output port, and incident light input from the input port. Is an arbitrary output port of the output ports of the input / output optical system via the second lens and the diffraction grating, for the light incident on the first lens and reflected by the deflection element according to the angle of the deflection element It is characterized by leading to.

  According to the present invention, the reflection surface is provided on the diffraction grating, and the third lens and the light receiving element are provided on the optical axis of the reflection light reflected by the reflection surface of the diffraction grating. By adopting a simple configuration, it is possible to easily measure the amount of reflected light of diffracted light, and as a result, it is possible to achieve downsizing and cost reduction.

[First Embodiment]
Hereinafter, a first embodiment according to the present invention will be described in detail with reference to the drawings.

<Wavelength selective optical switch>
As shown in FIGS. 1 and 2, the wavelength selective optical switch according to the present embodiment includes a fiber array 1, a microlens array 2, a condenser lens 3, a 4f optical system 4, and a MEMS mirror array chip. 5, a third lens 6, and a light receiving element array 7. Here, an incident direction of incident light from the fiber array 1 is a Z-axis direction, an arrangement direction of optical fibers constituting the fiber array 1 is a Y-axis direction, and a direction perpendicular to the Z-axis and the Y-axis is an X-axis direction. At this time, the first lens 41 and the diffraction grating 43, the third lens 6 and the light receiving element array 7 constituting the fiber array 1, the micro lens array 2, the condenser lens 3 and the 4f optical system 4 are in this order. They are arranged along the Z-axis direction. Further, the second lens 42 and the MEMS mirror array chip 5 constituting the 4f optical system 4 are arranged in the order from the diffraction grating 43 constituting the 4f optical system 4 along the X-axis direction. FIG. 2 is a schematic view of the optical system from the fiber array 1 to the MEMS mirror array chip 5 as seen from the YZ plane.

  The fiber array 1 has a configuration in which a plurality of optical fibers (seven in the case of FIG. 2) are juxtaposed in the Y-axis direction orthogonal to the Z-axis with the optical axis along the Z-axis. In FIG. 1, one input port 1a and six output ports 1b-1 to 1b-6 are provided.

  The microlens array 2 has a plurality of microlenses arranged in parallel along the Y direction. Such a microlens array 2 includes optical fibers of the fiber array 1 corresponding to the microlenses on the output side of the input port 1a and the input side of the output port 1b, that is, the positive side in the Z direction of the fiber array 1. It arrange | positions so that it may oppose.

The 4f optical system 4 includes a first lens 41 and a second lens 42 each having a focal length f ₁ , and a transmission type diffraction grating 43. The first lens 41 is disposed at a position separated from the condenser lens 3 by the sum of the focal length of the condenser lens 3 and the focal length f ₁ of the first lens 41. The diffraction grating 43 is disposed at a position separated from the first lens 41 by the focal length f ₁ . The second lens 42 is disposed at a position separated from the diffraction grating 43 by a focal length f _{1 in the} X-axis direction. Here, the plane composed of the X axis and Y axis at the focal point of the first lens 41 on the condenser lens 3 side is defined as the first focal plane, and the Z axis and Y at the focal point of the second lens 42 on the MEMS mirror array chip 5 side. A plane composed of the axes is referred to as a second focal plane. In the diffraction grating 43, the direction along the Y-axis is the q-axis direction, along the front or back surface of the diffraction grating 43, and the direction perpendicular to the q-direction is the p-axis direction, the front surface of the diffraction grating 43, and the q-direction. Let the perpendicular direction be r direction.

  As shown in FIG. 3, on the back surface of the diffraction grating 43 (on the MEMS mirror array chip 5 side), a grating portion 43a in which a large number of parallel slits are formed along the q direction, and a side portion of the grating portion are formed. And a reflecting portion 43b. The reflection portion 43b is created by depositing a reflection film made of a metal film or a dielectric multilayer film on the side portion of the grating portion 43a. In FIG. 3, the region where P> Pa is the grating portion 43a, and the region where P <Pa is the reflecting surface 43b. In this embodiment, a blazed transmission diffraction grating having a dispersion capability of 0.08 deg / nm with respect to the + 1st order diffracted light is used as the diffraction grating 43, and this is arranged so as to be demultiplexed in the XZ plane. The tilt is adjusted so that the diffracted optical axis and the incident optical axis are 90 degrees, that is, the outgoing diffracted optical axis is along the X axis.

  As shown in FIG. 4, the MEMS mirror array chip 5 includes a plurality of MEMS mirror elements 52 each having a mirror 52a on a base 51 that is substantially rectangular in plan view, and a straight line passing through the center of the mirror 52a is the longitudinal direction of the base 51. That is, it has the structure arranged along the Z-axis direction. Such a MEMS mirror array chip 5 is disposed on the second focal plane with the main surface of the mirror 52a of the MEMS mirror element 52 facing the second lens 42 of the 4f optical system 4. The mirror 52a of the MEMS mirror element 52 is supported with respect to the base 51 so as to be rotatable in two axial directions: a wavelength separation axis (Z axis) and a Y axis perpendicular to the Z axis. As a result, the output port is selected by rotating the mirror 52a around the Z axis (symbol α). Further, the attenuation level is controlled by rotating the mirror 52a about the Y axis (reference numeral β).

The third lens 6 is composed of a lens having a focal length of f ₂ , and is arranged at a position separated from the diffraction grating 43 by f _{2 in} the positive direction of the Z axis.

  The light receiving element array 7 has a configuration in which a plurality of light receiving elements 71 made of PD are arranged in the X direction. Such a light receiving element array 7 is disposed at a position separated from the third lens 6 by a predetermined distance in the positive direction of the Z axis.

<Operation of wavelength selective optical switch>
Next, the operation of the wavelength selective optical switch according to the present embodiment will be described with reference to FIGS.

  For example, when WDM signal light that is wavelength-separated by 40 waves (channels) at a wavelength channel interval of 100 GHz is input from the input port 1a, the WDM signal light is input to the microlens array 2, the condensing lens 3, and the first lens 41. Is incident on the surface of the diffraction grating 43, and is demultiplexed into 40 waves by the diffraction grating 43. Each of the demultiplexed channels is aligned on the Z axis of the second focal plane to form a beam waist. . Here, the diffraction grating 43 is inclined 45 degrees counterclockwise from the position perpendicular to the Z axis about the q axis, that is, the Y axis. For this reason, the signal light demultiplexed by the diffraction grating 43 proceeds in the X-axis direction, that is, in the direction of the MEMS mirror array chip 5. In addition, the channel pitch at this time is approximately 100 μm. At this beam waist position, a MEMS mirror array chip 5 in which MEMS mirror elements 51 are arranged at an appropriate pitch corresponding to each channel is arranged. As described above, the mirror 52a of the MEMS mirror element 52 is supported so as to be rotatable in the biaxial direction of the wavelength separation axis (Z axis) and the Y axis perpendicular to the Z axis with respect to the base 51. Yes. As a result, the output port is selected by rotating the mirror 52a around the Z axis (symbol α). Further, the attenuation level is controlled by rotating the mirror 52a about the Y axis (reference numeral β).

≪When attenuation level is 0≫
Here, FIG. 1 and FIG. 2 show an optical path when connecting to the output port 1b-6 with attenuation 0. FIG. λ1 is a wavelength channel corresponding to the design center wavelength of the diffraction grating, and the optical path is indicated by a thick solid line. λ2 is a wavelength channel different from λ1, and the path is indicated by a thick dotted line.

  The light beam reflected by the mirror 52a passes through the second lens 42 and is irradiated on the back surface of the diffraction grating 43 as shown in FIG. 5A (see symbol a). Here, the irradiation position of the light beam a with respect to the back surface of the diffraction grating 43 corresponds to the positions of the output ports 1b-1 to 1b-6, and is changed by the rotation of the MEMS mirror 52a around the Z axis. For example, as shown in FIG. 5B, when the reflected light is emitted from the output port 1b-1, the light beam is applied to the lowermost part in the negative direction of the q axis. On the other hand, when the reflected light is emitted from the output port 1b-6, the light beam is applied to the uppermost portion in the positive direction of the q axis. When the output ports 1b-1 to 1b-6 are not selected, the light beam is irradiated on the p-axis. In this way, the light beam of the reflected light reflected by the mirror 52a has its irradiation position with respect to the back surface of the diffraction grating 43 translated in the q-axis direction according to the corresponding output ports 1b-1 to 1b-6. Here, the irradiation position of the light beam on the diffraction grating 43 does not depend on the wavelength of the optical channel, and when the rotation of the MEMS mirror element 52 about the Z axis (selection of the output port) is the same angle, that angle A light beam is irradiated to the same position according to (output port).

  Here, on the back surface of the diffraction grating 43b, as shown in FIGS. 3, 5A, and 5B, a grating portion 43a and a reflective portion 43b are formed. For this reason, most of the light beam applied to the back surface of the diffraction grating 43 is applied to the grating portion 43a, is transmitted (diffracted) through the diffraction grating 43, and travels toward the output ports 1b-1 to 1b-6. On the other hand, the light beam irradiated to the reflecting portion 43b is reflected by the reflecting portion 43b and proceeds to the light receiving element array 7 side. In this way, the reflected light from the mirror 52a is branched into two beams by the back surface of the diffraction grating 43.

As an example, in FIG. 1 and FIG. 2, the principal ray of the light beam reflected by the reflecting portion 43b of the diffraction grating 43 is indicated by a thin solid line (λ1) and a thin dotted line (λ2). On the optical axis of these light beams, a third lens 6 having a focal length f ₂ is disposed at a position away from the diffraction grating 43 by f ₂ .

After being reflected by the MEMS mirror 52a, the light beam of λ1 returns at an angle of 45 degrees with respect to the back surface of the diffraction grating 43, and thus enters the third lens 6 perpendicularly. Therefore, the λ1 beam forms an image on the XY plane at the position f ₂ from the third lens 6 toward the light receiving element array 7 side.

On the other hand, since the λ2 beam is incident on the diffraction grating 43 at a non-45 degree angle, it is incident on the third lens 6 also non-perpendicularly. At this time, since the third lens 6 is arranged so that the diffraction grating 43 is positioned on the focal plane, the λ2 beam forms an image on the same XY plane as the λ1 beam. At this time, the imaging position is offset by ΔX _{2 on} the X axis. This ΔX ₂ completely coincides with the distance (ΔX ₁ ) between the MEMS mirrors 52a corresponding to each channel if f ₂ = f ₁ due to the symmetry of the optical system.

  Similarly, for all channels, the reflected light beams (thin lines) are focused on the XY plane, and these will be arranged at a known pitch. The light receiving element array 7 is disposed on the XY plane. The arrangement pitch of the light receiving elements 71 of the light receiving element array 7 is formed to be equal to the arrangement pitch of the light beams of the reflected light. Therefore, the light beam reflected by the reflecting portion 43b on the back surface of the diffraction grating 43 is introduced into the light receiving element 71 corresponding to each channel. Thereby, the light receiving element array 7 can measure the light intensity of each channel light independently.

  As described above, the irradiation position of the light beam on the diffraction grating 43 does not depend on the wavelength of the optical channel, and the rotation of the MEMS mirror element 52 about the Z axis (output port selection) is the same angle. Is irradiated with the light beam at the same position according to the angle (output port), but the light beam reflected by the reflecting portion 43b is also condensed by the third lens 6 and also corresponds to each wavelength channel. The light receiving element 71 is coupled.

≪When attenuation is executed≫
Next, a case where attenuation is executed by rotating the MEMS mirror in the β direction will be described with reference to FIGS. 6 and 7 are views from the XZ plane direction and the YZ plane direction, respectively, similarly to FIGS. 1 and 2, and λ1 and λ2 are indicated by solid lines and dotted lines, respectively.

  The light beam (λ1) reflected by the MEMS mirror 52a is not shown regardless of the amount of change in the β direction of the MEMS mirror 52a because the first lens 41 and the second lens 42 are confocal optical systems. As shown by the thick solid line 6, the light always enters the diffraction grating 43 at 45 degrees. At this time, the irradiation position of the light beam on the back surface of the diffraction grating 43 is shifted by Δd in the p direction as shown in FIG. As the amount of change in the rotation β around the Y axis is increased, Δd is also increased, and the amount of light hitting the reflecting portion 43b on the back surface of the diffraction grating 43 is increased. Therefore, the amount of light reflected by the reflecting portion 43b and coupled to the light receiving element 71 also increases.

  That is, as indicated by the symbol b in FIG. 9, the amount of light transmitted through the diffraction grating 43 decreases as the displacement of the rotation β around the Y axis of the MEMS mirror 52a increases. On the other hand, the light quantity of the light beam received by the light receiving element 71 increases as the displacement of the rotation β around the Y axis of the MEMS mirror 52a increases, as indicated by reference numeral c in FIG.

  From this, it can be understood that the output value from the light receiving element 71 directly corresponds to the attenuation amount. Therefore, by using the output value from the light receiving element 71 to feed back to the change amount of the MEMS mirror 52a, it becomes possible to control the attenuation level and realize a function as a VOA (Variable Optical Attenuator). can do. In addition, if the total loss of the optical system is known, it is possible to detect the amount of light passing through the wavelength selective optical switch, so that ALC (Auto Level Control) can also be realized.

  The same can be said for the light beam of another wavelength channel λ2. The light beam (λ2) is incident on the diffraction grating 43 at a non-45 degree angle, but the incident angle on the diffraction grating 43 is always constant regardless of the amount of change in the rotation β. Therefore, the light beam (λ2) collected by the third lens 6 is always coupled to the same light receiving element 71 regardless of the change amount of the rotation β. Therefore, the attenuation level can be measured independently for all wavelength channels.

  Thus, according to the present embodiment, the diffraction grating 43 is provided with the reflection portion 43b, and the diffracted light reflected by the MEMS mirror 52a is placed on the optical axis of the reflected light reflected by the reflection portion 43b of the diffraction grating 43. By adopting a simple configuration in which the lens 6 and the light receiving element 71 are provided, it is possible to easily measure the amount of reflected light of the diffracted light, and as a result, downsizing and cost reduction can be realized.

  Since the light beam reflected by the reflecting portion 43b is partial light cut by the reflecting surface 43b on the back surface of the diffraction grating 43, the beam shape does not become a simple elliptical shape. However, in the coupling to the light receiving element 71, as long as the light is condensed so as to be sufficiently small with respect to the light receiving area of the light receiving element 71, the beam shape may be disordered. If the beam cannot be made sufficiently small with respect to the light receiving area of the light receiving element 71, a light receiving element package in which a lens is provided immediately before each light receiving element 71 may be used. Or you may make it comprise the 3rd lens 6 from a some lens so that it may become an appropriate beam size.

  5A, 5B, and 8, the grating portion 43a and the reflecting portion 43b are formed on the same surface (back surface) of the diffraction grating 43. These are divided into the front surface and the back surface. You may make it form. For example, only the grating processing may be performed on the front surface, and a metal coating may be applied as a reflective portion 43b on a part of the back surface. As a result, it is not necessary to designate a region for performing the grating processing, and the manufacturing cost can be reduced.

  Moreover, as shown in FIG. 10, the reflection part 43b on the back surface of the diffraction grating 43 may be formed on both sides of the grating part 43a. In this case, a part of the reflected light can be guided to the light receiving element 71 regardless of the direction of rotation b around the Y axis of the MEMS mirror 52a. At this time, the relationship between the light receiving power at the light receiving element 71 and the rotational β displacement amount around the Y axis of the MEMS mirror 52a has a minimum point as shown in FIG. Therefore, it is possible to perform peak search control that maximizes the amount of light passing through the diffraction grating 43. In addition, the configuration has little influence on the disturbance of the input signal. Furthermore, since the blocked light quantity is measured, the light quantity can always be monitored even in a full block state where the ports are not coupled. Therefore, even if a drift occurs in the MEMS mirror 52a, the connection path can be appropriately restored. This is the same even when the MEMS mirror 52a is pulled in for some reason. If the signal light is input from the input port 1a, the correct path is always obtained even if the rotation angle of the MEMS mirror 52a becomes an abnormal value. Connection can be restored. Further, even when the lens is rotated about the Y axis for attenuation, the block light is always coupled to the light receiving element 71, so that it does not become stray light and the crosstalk performance of the system can be improved.

  In this embodiment, the case where the present invention is applied to a drop-type wavelength selective optical switch has been described as an example. However, the output ports 1b-1 to 1b-6 in FIGS. Needless to say, the output port 1a can be applied to an Add type wavelength selective optical switch. Even in this case, the propagation trajectory of the optical signal in the wavelength selective optical switch is the same as that of the drop-type wavelength selective optical switch shown in FIGS. 1 and 2 (or FIG. 6 and FIG. 7). .

[Second Embodiment]
Next, a second embodiment according to the present invention will be described. The present embodiment is different from the first embodiment described above in the configuration of the diffraction grating 43. Therefore, in the present embodiment, the same names and symbols are assigned to the same components as those in the first embodiment, and the description thereof is omitted as appropriate.

  In the diffraction grating 43 in the first embodiment described above, a part of the input signal light is also blocked by the reflection part 43b formed in a part thereof, so that the insertion loss slightly increases. Therefore, in the present embodiment, the configuration of the reflection portion 43b of the diffraction grating 43 has a configuration as shown in FIGS.

  A diffraction grating 43 shown in FIG. 12 is a transmission type diffraction grating in a drop-type wavelength selective optical switch, and on the back surface thereof, on a substantially cross in a plan view provided near the optical axis such as the p-axis and the q-axis. A grating part 43 a and regions excluding the grating part 43 a, that is, reflecting parts 43 b provided at the four corners of the diffraction grating 43 are formed. With such a configuration, the light beam input from the input port 1 a propagates to the MEMS mirror array 5 without being clipped by the reflecting portion 43 b on the diffraction grating 43. Since the MEMS mirror 52a rotates around the Z-axis so as to go to a desired port, the reflected light is shifted in the q direction on the diffraction grating 43, and a part of the light beam is irradiated to the reflecting portion 43b. It is coupled to the light receiving element 71 through the third lens 6. Thereby, an increase in insertion loss can be prevented.

  A diffraction grating 43 shown in FIG. 13 is a transmission type diffraction grating in an Add type wavelength selective optical switch. Contrary to the case of FIG. 12, reflection parts 43b are provided at both ends of the p-axis. The grating portion 43a is formed in the region. As a result, only the light beam output to the output port is clipped by the reflecting portion 43b on the diffraction grating 43, so that an increase in insertion loss can be suppressed.

  Each wavelength channel reflected by the reflecting portion 43b of the diffraction grating 43 shown in FIG. 13 is condensed at different positions on the focal plane XY plane of the third lens 6 in FIGS. The amount of light can be monitored for each wavelength channel.

[Third Embodiment]
Next, a third embodiment according to the present invention will be described. In the present embodiment, components equivalent to those in the first and second embodiments described above are given the same names and reference numerals, and description thereof will be omitted as appropriate.

  As shown in FIGS. 14A to 14C, the wavelength selective optical switch according to the present embodiment has a position of the light receiving element array 7 in the wavelength selective optical switch shown in the first embodiment. The total reflection mirror 8 is disposed on the light receiving element array 7 and the MEMS mirror array chip 5 is provided on the light receiving element array 7. Here, the light receiving element array 7 is arranged at a predetermined interval in the positive direction in the Y direction of the MEMS mirror array chip 5. The total reflection mirror 8 is a flat total reflection mirror, and is disposed in a state where the main surface is inclined along the XY plane by θ degrees clockwise around the X axis.

  The light beam reflected by the reflecting portion 43b of the diffraction grating 43 is reflected by the total reflection mirror 8, and again travels toward the reflecting portion 43b of the diffraction grating 43 and is reflected toward the MEMS mirror 52a. This reflected light (hereinafter referred to as re-reflected light) is collected by the second lens 42 and forms a spot in the vicinity of the MEMS mirror 52a. This beam spot is separated for each wavelength as in the case of the first embodiment. At this time, the total reflection mirror 8 is inclined by a certain angle θ around the X axis. Therefore, the beam spot group formed by the re-reflected light is formed at a position offset in the Y-axis direction with respect to the MEMS mirror array chip 5, that is, a position where the light receiving element array 7 is disposed. Therefore, the light beam of re-reflected light reflected by the total reflection mirror 8 is introduced into the light receiving element 71 corresponding to each channel. Thereby, the light receiving element array 7 can measure the light intensity of each channel light independently.

  As described above, the MEMS mirror array chip 5 and the light receiving element array 7 are arranged in the same YZ plane with an offset in the Y direction, so that both can be mounted in one package. The ability to package such an active device in one package is preferable in terms of high reliability by hermetic sealing, reduction in manufacturing cost, size reduction, and the like. In addition, both can be monolithically or hybridly integrated on one chip.

  When adopting the above-described configuration, if the distance from the diffraction grating 43 to the total reflection mirror 8 is ΔZ, the optical path length from the MEMS mirror 52a to the light receiving element 71 is 4f + 2ΔZ, and the 4f optical system is not formed. Therefore, the beam size of the re-reflected light on the light receiving surface of the light receiving element 71 is larger than the beam size on the MEMS mirror 52a, and therefore does not become a beam waist. However, by using a light receiving element array having a light receiving element 71 having a sufficiently large light receiving area, integrating a lens in each light receiving element 71, or using a concave mirror having a loose curvature instead of a total reflection mirror. The above-described problems relating to beam size and focus shift can be easily solved.

[Fourth Embodiment]
Next, a fourth embodiment according to the present invention will be described. In the present embodiment, the same components as those in the first to third embodiments are denoted by the same names and reference numerals, and description thereof will be omitted as appropriate.

  As shown in FIG. 15, the wavelength selective optical switch according to the present embodiment has a negative X-axis direction from the center of the diffraction grating 43 shown in the first embodiment, that is, the MEMS mirror array chip 5 and A diffraction grating 9 is provided on the opposite side, and a fourth lens 10 and a second light receiving element array 11 are provided in the emission direction of the diffracted light by the diffraction grating 9. Here, the diffraction grating 9 is arranged in a state where the central axis along the Y axis is rotated 45 degrees clockwise from the state where the main surface is along the XY plane. Such a diffraction grating 9 is not provided with a reflection portion as described above.

  Further, as shown in FIG. 16, the diffraction grating 43 is provided with a reflecting portion 43b on the front surface as well as the back surface as shown in the first embodiment. In the present embodiment, an example will be described in which the reflective portion 43b is provided in the vicinity of both ends in the p direction and the grating portion 43a is provided in other regions.

  According to the present embodiment, a part of the WDM signal light input from the input port 1a is not demultiplexed by the grating unit 43a on the surface of the diffraction grating 43, and the reflection unit 43b provided on the surface of the diffraction grating 43. And is guided to the second diffraction grating 9. Since the second diffraction grating 9 is not provided with a reflecting portion, the WDM signal light reflected by the diffraction grating 43 is demultiplexed. The demultiplexed light beams of the respective channels are collected by the fourth lens 10 and coupled to the corresponding light receiving elements of the second light receiving element array 11. The light intensity of the light beam coupled to the light receiving element is proportional to the light intensity of the WDM signal light input from the input port 1a, and is independent of the attenuation by the MEMS mirror 52a and the port selection function. Therefore, in this embodiment, the optical intensity of the input light to the wavelength selective optical switch can be measured for each channel. In the light receiving element array 7, as described in the first embodiment, the attenuation power is measured. Therefore, the light receiving element array 7 and the second light receiving element array 11 are used in combination. By doing so, it becomes possible to obtain the optical intensities of the input light and output light of the wavelength selective optical switch for all channels. As a result, the OCM required in the previous stage of the conventional wavelength selective optical switch module can be omitted, and the subsystem of the wavelength selective optical switch can be significantly reduced in size and cost. .

  Since the optical axes of the incident light to the light receiving element array 7 and the second light receiving element array 11 are parallel, these two light receiving element arrays can be mounted in one package. This is preferable in terms of high reliability by hermetic sealing, reduction in manufacturing cost, size reduction, and the like. Further, monolithic integration may be performed as a 2 × 40 array of PD arrays.

  Furthermore, as shown in FIG. 17, two total reflection mirrors 12 and 13 may be inserted in the subsequent stage of the diffraction grating 43 and the second diffraction grating 9 so that they can be moved in the X direction. Accordingly, it is possible to switch between the input-side OCM and the output-side OCM with one light receiving element array.

  In the first to fourth embodiments described above, a case where a MEMS mirror element is applied as an element for deflecting a demultiplexed wavelength channel has been described as an example. However, incident light is reflected and Various elements such as a liquid crystal spatial modulator can be applied as long as the deflecting element can control the reflection direction.

  The present invention can be applied to various apparatuses having a diffraction grating such as an optical channel monitor.

It is a figure from the XZ direction which shows the structure of the wavelength selection type optical switch which concerns on this invention. It is a figure from the YZ direction which shows the structure of the wavelength selection type optical switch which concerns on this invention. It is a perspective view which shows the structure of a diffraction grating. It is a front view which shows the structure of a MEMS mirror array chip. (A) The figure which shows the state of the back surface of the diffraction grating irradiated with reflected light, (b) The figure which shows the state of the back surface of the diffraction grating irradiated with the reflected light corresponding to each output port. It is a figure from the XZ direction which shows the structure of the wavelength selection type optical switch at the time of attenuation execution. It is a figure from the YZ direction which shows the structure of the wavelength selection type optical switch at the time of attenuation execution. It is a figure which shows the state of the back surface of the diffraction grating at the time of attenuation execution. It is a figure which shows the relationship between light intensity and the displacement of rotation (beta) around the Y-axis of a MEMS mirror. It is a figure which shows the modification of a diffraction grating. It is a figure which shows the relationship between the light intensity in the diffraction grating of FIG. 10, and the displacement of rotation (beta) around the Y-axis of a MEMS mirror. It is a figure which shows the modification of a diffraction grating. It is a figure which shows the modification of a diffraction grating. (A) The figure which shows the structure from the ZX direction of the wavelength selection type | mold optical switch provided with the total reflection mirror, (b) The figure from the ZY direction of (a), (c) The figure from the YX direction of (a). is there. It is a figure which shows the structure of the wavelength selection type optical switch provided with two diffraction gratings and two light receiving element arrays. It is a figure which shows the structure of the diffraction grating in FIG. It is a figure which shows the structure of the wavelength selection type optical switch provided with two movable total reflection mirrors. It is a figure which shows typically the structure of a wavelength selection type optical switch. It is a top view which shows the structure of the conventional MEMS mirror array chip | tip. It is a figure which shows typically the structure of the optical multiplexing / demultiplexing module which has an Add type wavelength selection type optical switch. It is a figure which shows typically the structure of the optical multiplexing / demultiplexing module which has a Drop type wavelength selection type optical switch.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fiber array, 1a ... Input port, 1b-1 to 1b-6 ... Output port, 2 ... Micro lens array, 3 ... Condensing lens, 4 ... 4f optical system, 5 ... MEMS mirror array chip, 6 ... 3rd 7 ... light receiving element array, 8 ... total reflection mirror, 9 ... diffraction grating, 10 ... second light receiving element array, 11 ... second light receiving element array, 12, 13 ... total reflection mirror, 41 ... first Lens, 42 ... 2nd lens, 43 ... Diffraction grating, 43a ... Grating part, 43b ... Reflection part, 51 ... Base part, 52 ... MEMS mirror element, 52a ... MEMS mirror.

Claims (10)

A first lens disposed on the optical axis of the incident light;
The first lens is disposed on the focal point on the opposite side of the incident light from the incident side, obliquely with respect to the optical axis of the incident light, and reflected on at least a part of the surface opposite to the first lens. A transmissive diffraction grating having a surface;
A second lens arranged on the optical axis of the diffracted light of the incident light diffracted by the diffraction grating and disposed so that one focal plane is located on the diffraction grating;
A deflecting element disposed on the optical axis of the diffracted light and on the other focal plane of the second lens, which reflects the diffracted light and guides it to the diffraction grating;
A third diffracted light reflected by the deflecting element is arranged on the optical axis of the reflected light reflected by the reflecting surface of the diffraction grating and so that one focal plane is located on the diffraction grating. With the lens
An optical channel monitor comprising: a light receiving element disposed on the optical axis of the reflected light and on the other focal plane side of the third lens. A first lens disposed on the optical axis of the incident light;
The first lens is disposed obliquely with respect to the optical axis of the incident light at a focal plane opposite to the incident light incident side of the first lens, and is reflected on at least a part of the surface opposite to the first lens. A transmissive diffraction grating having a surface;
A second lens arranged on the optical axis of the diffracted light of the incident light diffracted by the diffraction grating and disposed so that one focal plane is located on the diffraction grating;
A deflecting element disposed on the optical axis of the diffracted light and on the other focal plane of the second lens, which reflects the diffracted light and guides it to the diffraction grating;
A reflecting mirror disposed on the optical axis of the reflected light reflected by the reflecting surface of the diffraction grating, and the diffracted light reflected by the deflecting element;
An optical channel monitor comprising: a light receiving element disposed on an optical axis of the reflected light reflected by the reflecting mirror. A second diffraction grating disposed on the optical axis of incident light reflected by a reflection surface formed on a part of a surface of the diffraction grating facing the first lens;
A third lens arranged on the optical axis of the diffracted light diffracted by the second diffraction grating and so that the second diffraction grating is located on one focal plane;
The optical channel monitor according to claim 1, further comprising: a second light receiving element disposed on the other focal plane side of the third lens. Wherein the first diffraction grating is composed of arranged diffraction grating such that the Littrow arrangement of about 45 degrees with respect to primary or -1 order diffracted light,
The optical channel monitor according to any one of claims 1 to 3, wherein the diffracted light reflected by the deflecting element is incident on the diffraction grating at an angle of approximately 45 degrees. 5. The optical channel monitor according to claim 1, wherein the deflecting element includes a plurality of MEMS mirror elements arranged one-dimensionally. The diffraction grating has a grating portion in which a large number of slits are arranged in parallel to each other,
The optical channel monitor according to claim 1, wherein the reflection surface is formed in a band shape in the longitudinal direction of the slit at an end of the diffraction grating. The diffraction grating has a grating portion in which a large number of slits are arranged in parallel to each other,
The reflective surface is formed in the diffraction grating of generally rectangular plan view, both ends of the vertical end with respect to the longitudinal direction of the slit, or at a substantially central portion of the end parallel to the longitudinal direction of the slit The optical channel monitor according to claim 1, wherein the optical channel monitor is the optical channel monitor. The optical channel monitor according to claim 2, wherein the reflection mirror is disposed obliquely with respect to an optical axis direction of the reflected light. The optical channel monitor according to claim 2, wherein the reflection mirror includes a concave mirror. An optical channel monitor according to any one of claims 1 to 9,
An input / output optical system comprising at least one input port and at least one output port;
Incident light input from the input port is incident on the first lens;
The light reflected by the deflecting element according to the angle of the deflecting element is guided to an arbitrary output port of the input / output optical system via the second lens and the diffraction grating. Wavelength selective optical switch.

Images