Patent ID: 12207030

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in all the drawings in the present specification, constituent parts having corresponding functions are denoted by the same reference numerals, and the description thereof will be appropriately omitted.

Configuration of Embodiment

FIG.1is a block diagram illustrating a configuration of an OTN system using an optical node device according to an embodiment of the present invention.

An OTN system10A illustrated inFIG.1includes a plurality of optical node devices1aA,1bA, and1cA subordinately connected with optical fibers2. Each of the optical node devices1aA to1cA has the same configuration, and as shown representatively with example of the optical node device1bA inFIG.2, the optical node device includes beam splitters (branching units)21a,21b,21c, and21dfor branching by transmission and reflection of an optical signal, a separation wavelength selective switch (WSS)22, a multiplexing WSS23, a drop WSS24, an add WSS25, a monitoring transponder26, a transmission transponder27, a switch28, and an optical channel monitor29. The separation WSS22, the multiplexing WSS23, the drop WSS24, and the add WSS25are also referred to as WSSs22to25. The beam splitters21a,21b,21c, and21dare also referred to as beam splitters21.

These components21ato21dand22to29are connected with optical fibers as follows. That is, the beam splitter21ais connected to the separation WSS22and the switch28with the optical fiber, and the separation WSS22is connected to the multiplexing WSS23and the beam splitter21b. The multiplexing WSS23is connected to the beam splitters21cand21d. The beam splitter21bis connected to the drop WSS24and the switch28, and the beam splitter21cis connected to the add WSS25and the switch28.

The drop WSS24is connected to the monitoring transponder26, and the add WSS25is connected to the transmission transponder27. The switch28is connected to the optical channel monitor29.

In such a connection configuration, as illustrated inFIG.2, the beam splitter21atransmits an optical signal B1superimposed with a monitoring control signal M1transmitted from the external optical fiber2, outputs the optical signal B1to the separation WSS22, reflects the optical signal B1, and outputs the optical signal B1to the switch28. The monitoring control signal M1is a signal for performing optical path tracing that is confirmation of conduction along an optical path extended and set between the end points of the optical node devices1aA to1cA. The monitoring control signal M1multiplexes unique optical path identification (ID) information by intensity modulation that temporally changes the intensity of the optical signal B1.

As indicated by arrows M1a, M1b, M1c, M1d, M1e, and M1finFIG.1, the monitoring control signal M1can be superimposed on the optical signal B1in each of the WSSs22to25. This superimposition can be performed by modulating the optical signal B1with the monitoring control signal M1including the optical path ID information unique to each of the plurality of WSSs22to25.

Returning toFIG.2, the separation WSS22outputs the optical signal B1on which the monitoring control signal M1is superimposed to the multiplexing WSS23, separates the optical signal B1, and outputs the optical signal B1to the beam splitter21b. The beam splitter21btransmits and outputs the input monitoring control signal M1and the optical signal B1to the drop WSS24, and reflects and outputs the signals to the switch28.

The drop WSS24branches the monitoring control signal M1from the monitoring control signal M1and the optical signal B1according to the wavelength, and outputs the monitoring control signal M1to the monitoring transponder26. The monitoring transponder26measures and monitors optical power of the monitoring control signal M1. The monitor monitors whether the optical power is equal to or higher than a predetermined level indicating normality of the optical path.

The transmission transponder27outputs the optical signal B1to the add WSS25. The add WSS25modulates the optical signal B1with the monitoring control signal M1and outputs the modulated optical signal B1to the multiplexing WSS23via the beam splitter21c. The output monitoring control signal M1and optical signal B1are branched (reflected) by beam splitter21cand output to the switch28.

The multiplexing WSS23transmits the monitoring control signal M1and the optical signal B1from the separation WSS22to the external optical fiber2through the beam splitter21d. Alternatively, the multiplexing WSS23multiplexes the monitoring control signal M1and the optical signal B1output from the add WSS25and transmitted through the beam splitter21c, and transmits the multiplexed signals to the external optical fiber2through the beam splitter21d. In addition, the monitoring control signal M1and the optical signal B1output from the add WSS25are reflected by the beam splitter21cand output to the switch28.

The switch28selects the monitoring control signal M1from each of the beam splitters21ato21dand outputs the monitoring control signal M1to the optical channel monitor29. The optical channel monitor29reads the temporal change of the optical power of the monitoring control signal M1and demodulates the optical path ID information. The optical channel monitor29detects that the optical path is extended normally as will be described later based on the optical path ID information obtained by the demodulation.

For example, the optical channel monitor29holds unique information of the beam splitters21ato21dconnected to the switch28, and it can be detected by which beam splitter21the switch28inputs the monitoring control signal M1including the branched optical path ID information. With this function, the optical channel monitor29detects the WSSs22to25on which the monitoring control signals M1ato M1f(FIG.1) including the optical path ID information are superimposed and the beam splitters21ato21dbranching the monitoring control signals M1ato M1fimmediately before the switch28based on the optical path ID information. By this detection, the normality of the optical path between the WSSs22to25and the beam splitters21ato21dcan be confirmed (or detected).

Configuration Example of WSS

Here, a specific configuration example of each of the WSSs22to25having the same configuration is illustrated inFIG.3as a representative of the multiplexing WSS23, and the description thereof will be made.

The multiplexing WSS23illustrated inFIG.3includes an input fiber collimator (also referred to as a collimator)61, output collimators62aand62b, which are N times the number of input collimators61(for example, twice), a grating (diffraction grating)65that demultiplexes an optical signal subjected to wavelength division multiplexing, a lens67, and a spatial light modulator68including, for example, liquid crystal on silicon (LCOS). The input collimator61and the output collimators62aand62bare connected to the optical fiber. Note that the input collimator61includes the input collimator according to the claims. The output collimators62aand62binclude an output collimator according to the claims.

In such a configuration, the optical signal B1from the optical fiber is incident on the grating65via the collimator61as indicated by an arrow i1. The grating65diffracts and reflects the optical signal B1at different angles according to the wavelength to perform demultiplexing (for example, three-demultiplexing) as indicated by arrows i1a, i1b, and i1c. The three-demultiplexed optical signal is incident on the spatial light modulator68via the lens67.

The spatial light modulator68reflects the three-demultiplexed optical signal. At this time, a voltage B1V (referred to as a monitoring control voltage B1V) of the monitoring control signal M1is applied to the spatial light modulator68to apply intensity modulation. The optical signal B1on which the monitoring control signal M1is superimposed by the intensity modulation is output from the collimator62afor desired output via the lens67and the grating65as represented by an arrow o2as a representative of the1optical signal.

As indicated by the arrows i1cand o2, the optical signal is reflected by the spatial light modulator68. As illustrated inFIG.4, by changing the reflection angle from an angle θ2to an angle θ1smaller than the angle θ2, the efficiency when the optical signal is coupled to the output-side collimator62acan be changed to be small. The attenuation amount of the optical signal B1can be varied to be small according to the variation.

That is, when the monitoring control voltage B1V whose level changes with time is applied to the spatial light modulator68, a phase slope71that changes the reflection angle changes. The phase slope71changes according to a phase line c2or c1indicated by the pixel position of the axis (first axis) along the pixels of the spatial light modulator68in an arrangement direction and the value of “phase/2π” of the second axis orthogonal to the first axis. According to the monitoring control voltage B1V, the phase line c2gradually increases from 0, the value of “phase/2π” becomes the maximum value of φ2at the pixel position t1, and rapidly decreases from φ2 to 0, and then gradually increases again to become the maximum value of φ2 at a position t2. This operation is repeated.

The input optical signal B1indicated by the arrow i1is reflected by the reflection angle θ2corresponding to the phase line c2, and is output to the output-side collimator62aas indicated by the arrow o2. The attenuation amount of the optical signal B1in the collimator62ais indicated by a mountain-shaped curve72a.

On the other hand, when the level of the applied monitoring control voltage B1V becomes lower than the above level, the phase line c1indicated by the broken line gradually increases from 0, and the value of “phase/2π” becomes the maximum value of o1smaller than φ2 at the pixel position t1. Further, the phase line c1rapidly decreases from φ1 to 0, and then gradually increases again to become the maximum value of φ1 at the position t2. This operation is repeated.

In the phase line c1, the reflection angle θ1is smaller than the reflection angle θ2. The optical signal B1indicated by the arrow o1obtained by reflecting the input optical signal B1of the arrow i1at the angle θ1is output to the output-side collimator62a. At this time, the attenuation amount (for example, 80%) of the optical signal B1indicated by the arrow o1is the amount indicated by the curve72b, and deviates to be smaller than the attenuation amount (for example, 90%) indicated by the curve72aof the optical signal B1indicated by the arrow o2.

Operation of Embodiment

Next, the operation of the optical path tracing in the OTN system10A according to the present embodiment will be described with reference to the flowcharts ofFIGS.5and6. However, as illustrated inFIG.1, it is assumed that an optical path P3is extended between the transmission transponder27(start point) of the optical node device1aA and the monitoring transponder26(end point) of the optical node device1cA while relaying the optical node device1bA.

Specifically, the optical path P3extends from the transmission transponder27of the optical node device1aA to the beam splitter21aof the optical node device1bA through the add WSS25, the beam splitter21c, the multiplexing WSS23, and the beam splitter21dvia the optical fiber2. Further, the optical path P3reaches the beam splitter21aof the optical node device1cA through the separation WSS22, the multiplexing WSS23, and the beam splitter21dof the optical node device1bA via the optical fiber2. Further, the optical path P3reaches the monitoring transponder26through the separation WSS22, the beam splitter21b, and the drop WSS24of the optical node device1cA.

In step S1illustrated inFIG.5, the optical signal B1transmitted from the transmission transponder27is output to the add WSS25via the optical path P3.

In step S2, it is assumed that the monitoring control signal M1aincluding the optical path ID information a is superimposed on the optical signal B1by the add WSS25. At the time of this superimposition, unique information of the add WSS25of the optical node device1aA is also added.

In step S3, the optical signal B1(referred to as a superimposed optical signal) on which the monitoring control signal M1ais superimposed is transmitted to the monitoring transponder26of the optical node device1cA via the optical path P3via the optical node device1bA.

In step S4, it is determined whether the superimposed optical signal has been transmitted by all the beam splitters21through which the optical path p3passes. This determination is made when the monitoring transponder26at the end point detects the monitoring control signal M1afrom the superimposed optical signal.

As a result of this determination, if all the beam splitters21through which the optical path P3passes transmit (Yes), the monitoring transponder26measures and monitors the optical power of the monitoring control signal M1ain step S5. The monitor monitors whether the optical power is equal to or higher than a predetermined level indicating normality of the optical path. By checking this display, the NW administrator can grasp the normality of the entire optical path P3between the transmission transponder27at the start point and the monitoring transponder26at the end point that relays the optical node device1bA.

On the other hand, in a case where in step S4, it is determined that the superimposed optical signal is not transmitted through all the beam splitters21(No), it is determined in step S6ofFIG.6whether the superimposed optical signal is branched by reflection at the beam splitter21don the most starting point side of the optical path P3.

As a result of the determination, when it is determined as branched (Yes), in step S7, the branched superimposed optical signal is output to the switch28as indicated by a broken line arrow Y1ainFIG.1.

In step S8, in the switch28, the monitoring control signal M1ais selected and output to the optical channel monitor29as indicated by a dashed arrow Y1b.

In Step S9, the optical channel monitor29reads the temporal change of the optical power of the monitoring control signal M1aand demodulates the optical path ID information a. Further, the optical channel monitor29detects the optical path P3between the add WSS25and the beam splitter21dbased on the optical path ID information a, and detects (monitors) normality of the detected optical path P3.

In step S10, it is determined whether there is the beam splitter21on the next subsequent stage side in the optical path P3. This determination is made when the optical channel monitor29detects the monitoring control signal M1abranched by the next beam splitter21. If it can be detected, it is determined that there is the beam splitter, and if it cannot be detected, it is determined that there is no beam splitter. As a result of this determination, since there is the beam splitter21aof the next optical node device1bA, the process returns to Step S6. On the other hand, in a case where there is no beam splitter, the optical path trace process is terminated.

That is, in step S6, the optical channel monitor29determines whether the superimposed optical signal is branched by the beam splitter21aof the next optical node device1bA.

As a result of the determination, when it is determined as branched (Yes), in step S7, the branched superimposed optical signal is output to the switch28as indicated by a broken line arrow Y2a.

In step S8, in the switch28, the monitoring control signal M1ais selected and output to the optical channel monitor29as indicated by a dashed arrow Y2b.

In Step S9, the optical channel monitor29reads the temporal change of the optical power of the monitoring control signal M1aand demodulates the optical path ID information a, and the add WSS25, and the optical path ID information a of the beam splitter21a. Further, the optical channel monitor29detects the optical path P3between the add WSS25and the beam splitter21abased on the optical path ID information a, and detects (monitors) normality of the detected optical path P3.

In step S10, the optical channel monitor29determines whether there is the beam splitter21on the next subsequent stage side in the optical path P3. As a result of this determination, since there is the beam splitter21dof the next optical node device1bA, the process returns to Step S6.

That is, in step S6, it is determined whether the superimposed optical signal is branched by the beam splitter21dof the next optical node device1bA.

As a result of the determination, when it is determined as branched (Yes), in step S7, the branched superimposed optical signal is output to the switch28as indicated by a broken line arrow Y2c.

In step S8, in the switch28, the monitoring control signal M1ais selected and output to the optical channel monitor29as indicated by a dashed arrow Y2b.

In Step S9, the optical channel monitor29reads the temporal change of the optical power of the monitoring control signal M1aand demodulates the optical path ID information a, and the add WSS25, and the optical path ID information a of the beam splitter21d. Further, the optical channel monitor29detects the optical path P3between the add WSS25and the beam splitter21dbased on the optical path ID information a, and detects (monitors) normality of the detected optical path P3.

In step S10, it is determined whether there is the beam splitter21on the next subsequent stage side in the optical path P3. As a result of this determination, since there is the beam splitter21aof the next optical node device1cA, the process returns to Step S6.

That is, in step S6, it is determined whether the superimposed optical signal is branched by the beam splitter21aof the next optical node device1cA.

As a result of the determination, when it is determined as branched (Yes), in step S7, the branched superimposed optical signal is output to the switch28as indicated by a broken line arrow Y3a.

In step S7, in the switch28, the monitoring control signal M1ais selected and output to the optical channel monitor29as indicated by a dashed arrow Y3b.

In Step S8, the optical channel monitor29reads the temporal change of the optical power of the monitoring control signal M1aand demodulates the optical path ID information a, and the add WSS25, and the optical path ID information of the beam splitter21a. Further, the optical channel monitor29detects the optical path P3between the add WSS25and the beam splitter21abased on the optical path ID information a, and detects (monitors) normality of the detected optical path P3.

In step S10, it is determined whether there is the beam splitter21on the next subsequent stage side in the optical path P3. As a result of this determination, since there is the beam splitter21bof the next optical node device1cA, the process returns to Step S6.

That is, in step S6, it is determined whether the superimposed optical signal is branched by the beam splitter21bof the next optical node device1cA.

As a result of the determination, when it is determined as branched (Yes), in step S7, the branched superimposed optical signal is output to the switch28as indicated by a broken line arrow Y3c.

In step S8, in the switch28, the monitoring control signal M1ais selected and output to the optical channel monitor29as indicated by a dashed arrow Y3b.

In Step S9, the optical channel monitor29reads the temporal change of the optical power of the monitoring control signal M1aand demodulates the optical path ID information a, and the add WSS25, and the optical path ID information a of the beam splitter21b. Further, the optical channel monitor29detects the optical path P3between the add WSS25and the beam splitter21bbased on the optical path ID information a, and detects (monitors) normality of the detected optical path P3.

In step S10, it is determined whether there is the beam splitter21on the next subsequent stage side in the optical path P3. As a result of this determination, since there is no next beam splitter21, the optical path trace process is terminated.

Effects of Embodiment

(1a) An optical node device1aA to1cA includes a transmission transponder27, WSSs22to25, a beam splitter21, and a monitoring transponder26. The transmission transponder27transmits an optical signal B1via an optical path P3extended over an optical fiber2. The WSSs22to25multiplex, on the transmitted optical signal B1, a monitoring control signal M1for performing optical path tracing that is confirmation of conduction along the optical path P3.

The beam splitter21branches the optical signal B1in which the monitoring control signal M1is multiplexed. The monitoring transponder26measures and monitors the optical power of the monitoring control signal M1multiplexed on the optical signal B1branched by the beam splitter21. Further, the monitoring transponder26is configured to monitor whether the monitored optical power is equal to or higher than a predetermined level indicating the normality of the optical path P3.

According to this configuration, the optical node device1bA can determine the normality of the optical path P3from the optical power of the monitoring control signal M1multiplexed with the optical signal B1transmitted from the other optical node device1aA. Since the normality of the optical path P3is determined by the dedicated monitoring control signal M1, it is possible to appropriately determine the abnormality of the optical path P3set between the optical node devices1aA and1cA. In addition, also in the optical node device1bA that relays the optical path P3between the optical node devices1aA and1cA, the normality of the optical path P3can be determined by the optical node device1bA for relaying, so that the optical path tracing can be appropriately performed.

(2a) The WSSs22to25include an optical channel monitor29that performs multiplexing including unique optical path ID information when the monitoring control signal M1is multiplexed into the optical signal B1and monitors the optical path ID information obtained by reading and demodulating a temporal change of optical power of the monitoring control signal M1multiplexed into the optical signal B1branched by the beam splitter21. The optical channel monitor29is configured to detect normality of the optical path P3between the transmission transponder27and the beam splitter21that has branched the optical signal B1based on the optical path ID information.

According to this configuration, it is possible to confirm the normality of the optical path P3between the start point and the beam splitter21disposed in the middle between the transmission transponder27at the start point for transmitting the optical signal B1and the monitoring transponder26at the end point for receiving the optical signal B1.

(3a) The WSSs22to25include an input collimator61to which the optical signal B1is input, a diffraction grating65that receives the optical signal B1through the input collimator61, diffracts the optical signal at a different angle according to a wavelength of the optical signal B1, reflects the optical signal, and demultiplexes the optical signal, a spatial light modulator68that reflects the demultiplexed optical signal B1and applies a voltage B1V of the monitoring control signal M1to the optical signal B1at the time of reflection to apply intensity modulation, and an output collimator62athat outputs the optical signal B1reflected by the spatial light modulator68.

According to this configuration, the WSSs22to25can be configured by an optical system component obtained by combining the input and output collimators, the diffraction grating, and the spatial light modulator. Therefore, it is possible to reduce the size of the optical node devices1aA to1cA including the WSSs22to25.

(4a) The OTN system10A has a configuration in which the optical node devices1aA to1cA described in any one of (1a) to (3a) above are subordinately connected by the optical fiber2via the beam splitter21.

According to this configuration, in the optical node devices1aA to1cA at both ends to which the optical path P3is extended, the normality of the optical path P3can be determined from the optical power of the monitoring control signal M1multiplexed with the optical signal B1transmitted through the optical path P3. This determination can appropriately determine the abnormality of the optical path P3based on the dedicated monitoring control signal M1. In addition, also in the optical node devices1aA to1cA that relay the optical path P3between the optical node devices1aA and1cA, the normality of the optical path P3can be determined by the optical node devices1aA to1cA for relaying, so that the optical path tracing can be appropriately performed.

(5a) The OTN system10A is configured to multiplex the monitoring control signal M1with unique optical path ID information into the optical signal B1to be transmitted on the optical path P3in each of the WSSs22to25on the optical path P3extended between the optical node devices1aA to1cA subordinately connected.

According to this configuration, in the arbitrary WSSs22to25, the monitoring control signal M1having the unique optical path ID information can be multiplexed into the optical signal B1. Therefore, it is possible to confirm the normality of the optical path P3in an arbitrary section such as the optical path P3between the WSSs22to25of the desired optical node devices1aA to1cA and the beam splitter21of the other optical node devices1aA to1cA, the optical path P3between the transmission transponder27at the start point and the WSSs22to25of the desired optical node devices1aA to1cA, and the optical path P3between the WSSs22to25of the desired optical node devices1aA to1cA and the monitoring transponder26at the end point.

In addition, a program executed by the computer according to the present embodiment will be described. The computer is assumed to be an optical node device {for example, an optical node device1aA (FIG.1)}.

This program causes the computer to function as: means for transmitting an optical signal B1via an optical path P3extended over the optical fiber, means for multiplexing, on the transmitted optical signal B1, a monitoring control signal M1for performing optical path P3tracing that is confirmation of conduction along the optical path P3, means for branching the optical signal B1in which the monitoring control signal M1is multiplexed, means for measuring and monitoring optical power of the monitoring control signal M1multiplexed into the optical signal B1, and means for monitoring whether the monitored optical power is equal to or higher than a predetermined level indicating normality of the optical path P3.

According to this program, effects similar to the effects of the optical node devices1aA to1cA described above can be obtained.

<Effects>

(1) An optical node device including a transmission transponder that transmits an optical signal via an optical path extended over an optical fiber, a wavelength selective switch (WSS) that multiplexes, on the transmitted optical signal, a monitoring control signal for performing optical path tracing that is confirmation of conduction along the optical path, a branching unit that branches the optical signal in which the monitoring control signal is multiplexed, and a monitoring transponder that measures and monitors optical power of the monitoring control signal multiplexed into the optical signal branched by the branching unit, in which the monitoring transponder monitors whether the monitored optical power is equal to or higher than a predetermined level indicating normality of the optical path.

According to this configuration, the optical node device can determine the normality of the optical path from the optical power of the monitoring control signal multiplexed with the optical signal transmitted from the other optical node device. Since the normality of the optical path is determined by the dedicated monitoring control signal, it is possible to appropriately determine the abnormality of the optical path set between the optical node devices. In addition, also in the optical node device that relays the optical path between the optical node devices, the normality of the optical path can be determined by the optical node device for relaying, so that the optical path tracing can be appropriately performed.

(2) The optical node device described in above (1), in which the WSS includes an optical channel monitor that, when multiplexing the monitoring control signal with the optical signal, multiplexes the monitoring control signal including unique optical path identification (ID) information, and monitors the optical path ID information obtained by reading and demodulating a temporal change of the optical power of the monitoring control signal multiplexed on the optical signal branched by the branching unit, and the optical channel monitor monitors the normality of the optical path between the transmission transponder and the branching unit branching the optical signal based on the optical path ID information.

According to this configuration, it is possible to confirm the normality of the optical path between the start point and the branching unit disposed in the middle between the transmission transponder at the start point for transmitting the optical signal and the monitoring transponder at the end point for receiving the optical signal.

(3) The optical node device described in any one of above (1) to (3), in which the WSS includes an input collimator to which the optical signal is input, a diffraction grating that receives the optical signal through the input collimator, diffracts the optical signal at a different angle according to a wavelength of the optical signal, reflects the optical signal, and demultiplexes the optical signal, a spatial light modulator that reflects the demultiplexed optical signal and applies a voltage of the monitoring control signal to the optical signal at the time of reflection to apply intensity modulation, and an output collimator that outputs the optical signal reflected by the spatial light modulator.

According to this configuration, the WSSs can be configured by an optical system component obtained by combining the input and output collimators, the diffraction grating, and the spatial light modulator. Since the similar WSS of a multiple-output type with one input exists in a general-purpose type, the WSS of the present embodiment can be easily created by using the WSS.

(4) An optical transport network system, in which the optical node device described in any one of above (1) to (3) is subordinately connected by an optical fiber via the branching unit.

According to this configuration, in the optical node devices at both ends to which the optical path is extended, the normality of the optical path can be determined from the optical power of the monitoring control signal multiplexed with the optical signal transmitted through the optical path. This determination can appropriately determine the abnormality of the optical path based on the dedicated monitoring control signal. In addition, also in the optical node device that relays the optical path between the optical node devices, the normality of the optical path can be determined by the optical node device for relaying, so that the optical path tracing can be appropriately performed.

(5) The optical transport network system described in above (4), in which a monitoring control signal with unique optical path ID information is multiplexed into an optical signal to be transmitted on the optical path in each of the WSSs on the optical path extended between the subordinately connected optical node device.

According to this configuration, in the arbitrary WSSs, the monitoring control signal having the unique optical path ID information can be multiplexed into the optical signal. Therefore, it is possible to confirm the normality of the optical path in an arbitrary section such as the optical path between the WSS of the desired optical node device and the branching unit of another optical node device, the optical path between the transmission transponder at the start point and the WSS of the desired optical node device, and the optical path between the WSS of the desired optical node device and the monitoring transponder at the end point.

In addition, the specific configuration can be appropriately changed without departing from the gist of the present invention.

REFERENCE SIGNS LIST

1aA to1cA Optical node device10A OTN system21ato21dBeam splitter (branching unit)22Separation WSS23Multiplexing WSS24Drop WSS25Add WSS26Monitoring transponder27Transmission transponder28Switch29Optical channel monitorP3Optical path61Input fiber collimator62a,62bOutput fiber collimator65Grating (diffraction grating)67Lens68Spatial light modulatorB1V Monitoring control voltage