JP5975855B2 - Discrete optical path length adjustment device - Google Patents

Description

The present invention relates to an optical path length adjustment technique for changing the optical path length of the light path at a predetermined interval length, relates in particular to a discrete optical path length adjusting equipment for the optical path length of the light path, with duplication is adjusted to be the same .

  In recent years, the communication line has been transferred from the existing transmission line to the detour transmission line without disrupting the communication service in the troubled transfer work of the optical line, etc. Service uninterrupted switching technology has been developed that enables trouble transfer work and the like without disrupting the communication service by returning the transmission path to the existing transmission path. This technology prepares a detour transmission path, duplexes the existing transmission path and the temporary communication line, and then stops the communication light of either the existing transmission path or the detour transmission path. This is a method of switching communication lines while moving. However, simply duplicating the line causes optical interference due to the optical phase shift, and thus the communication service cannot be maintained. Therefore, an optical path length adjustment technique for keeping the optical path length difference between the working transmission path and the bypass transmission path within a predetermined allowable range is indispensable.

  As the conventional optical path length adjusting devices, there are m sets of optical fiber pairs in which an optical path length difference is given by multiplying a power of 2 by a unit length between a pair of wavelength independent couplers (WICs). There is an optical path length adjusting device having a configuration in which m + 1 2 × 2 optical switches are interposed and connected in series (see Non-Patent Document 1).

  However, this technique has a problem in that fixed delays generated by individual optical switches are accumulated in proportion to the number of optical switches to be used. Since the accumulation of fixed delays leads to an increase in the minimum optical path length, it is an important problem in this apparatus that the proposition is to widen the variable optical path length (maximum optical path length-minimum optical path length).

Yoshida et al .: Examination of service-less uninterruptible optical medium switching technology using polarization maintaining optical switch, IEICE technique OFT2011-02-25, vol.110 (436), pp.21-26,2008 Higashi et al .: Fundamental study of optical access media switching system-Service uninterrupted optical media switching system-, IEICE Tech.

As described above, the conventional discrete optical path length adjusting device has a problem in that the fixed delay generated by each optical switch is accumulated in proportion to the number of optical switches to be used.
The present invention has been made paying attention to the above circumstances, and the purpose thereof is to suppress the accumulation of fixed delays even when the number of optical switches increases, thereby reducing the overall delay time. and to provide a discrete optical path length adjusting equipment capable of wider optical path length variable region.

In order to achieve the above object, a discrete optical path length adjusting device according to the present invention is configured as follows.
(1) In a discrete optical path length adjusting device that changes the delay time of an optical signal, a plurality of delay optical fibers whose optical path lengths are sequentially given by multiplying a power of 2 by a unit length and the plurality of delay optical fibers are selectively used A plurality of switching optical switch means connected in series to generate an arbitrary delay time, a selection optical switch means for selecting and outputting an arbitrary output among the plurality of switching optical switch means, and the plurality of switching lights Control means for controlling switching of the switch means and selection of the selection light switch means, wherein the plurality of switch light switch means selectively connects the plurality of delay optical fibers in series and outputs any one of them. A 3 × 3 optical switch having a port as an external output port, wherein the selection optical switch means outputs any one of the external output ports of each of the 3 × 3 optical switches. The control means selectively switches the plurality of switching optical switch means in accordance with a designated delay time to connect the delay optical fibers in series, and outputs the delay optical fiber in the final stage. The selection light is switched by the selection light switch means.

( 2 ) In a discrete optical path length adjusting device that changes a delay time of an optical signal, a plurality of delay optical fibers whose optical path lengths are given in order by multiplying a power of 2 by a unit length and the plurality of delay optical fibers are selectively used A plurality of switching optical switch means connected in series to generate an arbitrary delay time, a selection optical switch means for selecting and outputting an arbitrary output among the plurality of switching optical switch means, and the plurality of switching lights Control means for controlling switching of the switch means and selection of the selection optical switch means, and the plurality of delay optical fibers are selectively connected to an optical fiber giving an offset of unit length × 1/2 length The control means selectively switches the plurality of switching optical switch means in accordance with a designated delay time to connect the delay optical fibers in series, and outputs the output of the final stage delay optical fiber. And embodiments by the selection optical switch means Ru is selected output.

In other words, the present invention realizes a reduction in the fixed delay by making it possible to select the optical output using the selective light switch means. In other words, the optical switch is added to the following optical switch in addition to the path going to the next optical switch through the delay optical fiber for adjusting the optical path length and the path going to the next optical switch without passing through the delay optical fiber. This makes it possible to select a path (short circuit path) for direct output by skipping the connection, thereby eliminating unnecessary fixed delay accumulation. Therefore, according to the present invention, even when the number of optical switches increases, it is possible to suppress the accumulation of fixed delays, thereby realizing a reduction in the overall delay time and a discrete optical path variable range that can be widened. it is possible to provide a specific optical path length adjusting equipment.

1 is an optical circuit diagram showing a configuration of a first embodiment of an optical path length adjusting device according to the present invention. The optical circuit diagram which shows the switching mode of the 3x3 port optical switch used for 1st Embodiment. The flowchart which shows the optical path length setting process of 1st Embodiment. The optical circuit diagram which shows the structure of 2nd Embodiment of the optical path length adjustment apparatus which concerns on this invention. The optical circuit diagram which shows the switching mode of the 2 * 2 port optical switch used for 2nd Embodiment. The optical circuit diagram which shows the structure of 3rd Embodiment of the optical path length adjustment apparatus which concerns on this invention. The optical circuit diagram which shows the switching mode of the 2 * 2 port optical switch used for 3rd Embodiment. The optical circuit diagram which shows the structure of 4th Embodiment of the optical path length adjustment apparatus which concerns on this invention.

Embodiments according to the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing a configuration of a first embodiment of a discrete optical path length adjusting device according to the present invention. In FIG. 1, reference numerals 11 and 12 denote wavelength-independent optical couplers (WICs) 161 to 16 (m + 1) for bifurcating an optical line 13 by an optical fiber into an A-system optical line 14 and a B-system optical line 15. 171~17 (m + 1), respectively a, the B lineage respective optical line 14 and 15, the optical path length of ^{2 0, 2 1, 2 2} , ..., 2 m-1 unit length a power of 2 represented by l A 3 × 3 port optical switch (hereinafter referred to as a 3 × 3 optical switch) that selectively connects both ends of m optical fibers given by ₀ in response to a control instruction from the control device 20. 3 and 3 are collectively referred to as 3 × 3 optical switch groups 16 and 17), 18 and 19, respectively, according to control instructions from the control device 20, optical switches 161 to 16 (m + 1) and 171 to 17 for the A and B systems, respectively. N × 1 for extracting one of the selected outputs of (m + 1) Port optical switch (N is 1 to m + 1, hereinafter referred to as N × 1 optical switch).

  That is, in the adjusting device having the above-described configuration, a pair of wavelength-independent optical couplers 11 and 12 is used to provide a 3 × 3 port optical switch group 16 and 17 and N × 1 optical switches 18 and 19 having a small wavelength dependency. , B systems are combined with an optical path length adjustment unit by an optical line to form a duplex optical line.

2A to 2I show all switching modes of the 3 × 3 optical switch. 2A to 2I, SW is a 3 × 3 optical switch, I ₁ is a first input port, I ₂ is a second input port, I ₃ is a third input port, and O ₁ is a _first input port. 1 is an output port, O ₂ is a second output port, and O ₃ is a third output port. As shown in FIG. 2, the 3 × 3 optical switch SW has nine switching modes for coupling three input ports and three output ports. However, the internal optical path difference in the nine switching modes can be ignored.

The first output port O ₁ and the (n + 1) th 3 × 3 optical switch 16 (n + 1) of the nth 3 × 3 optical switch 16 n and 17 n of each of the A system optical line 14 and the B system optical line 15, 17 (n + 1) first input port _{I 1} 3 × 3 of the optical path length and n-th optical fiber connects the optical switch 16n, a second output port _{O 2} and n + 1 th 3 × 3 of 17n of The optical path lengths of the optical fibers connecting the _second input ports I2 of the optical switches 16 (n + 1) and 17 (n + 1) differ by a unit length l ₀ × 2 ⁿ⁻¹ . Input / output ports not used in this configuration are terminated with no reflection.

The 3 × 3 optical switches 161 to 16 (m + 1) and 171 to 17 (m + 1) of each system are respectively connected to N × 1 optical switches 18 and 19 by optical fibers of an arbitrary length, and these N × 1 optical switches 18 , 19, only the optical signals from the 3 × 3 optical switches 161 to 16 (m + 1) and 171 to 17 (m + 1) are output. In order to easily improve the resolution, an optical fiber that gives an offset having a unit length l ₀ × 1/2 may be connected to the A system or the B system.

Next, an optical path length setting method in the present embodiment will be described with reference to a control flow for the optical path length adjustment unit of the control device 20 shown in FIG.
First, as a precondition, the maximum variable optical path length using only the optical path length difference between the optical switches up to the nth 3 × 3 optical switches 16n and 17n is Tv (n), and the nth 3 × 3 optical switch 16n. , 17n and the fixed delay amount of the nth 3 × 3 optical switches 16n, 17n to the N × 1 optical switches 18, 19 are expressed as Tf (n), the nth 3 × 3 The set optical path length to the optical switches 16n and 17n is T (n). The magnitude relationship of the fixed delay amount Tf (n) is
Tf (n + 1) ≧ Tf (n) (1)
Suppose that However, 1 ≦ n ≦ m (m is the total number of 3 × 3 optical switches of A system or B system). In order to continuously adjust the optical path length at unit length intervals,
Tv (n) ≧ Tf (n + h) −Tf (n) (2)
It is necessary to satisfy. However, 2 ≦ n ≦ m−1.

In the present embodiment, it is assumed that Expression (2) is satisfied. When Expression (2) is satisfied, the input to the N × 1 optical switches 18 and 19 is the n + h th 3 × 3 optical switches 16 (n + h) and 17 (n) from the outputs of the n th 3 × 3 optical switches 16n and 17n. n + h). Therefore, the minimum fixed delay amount Tmin of the optical path length adjustment unit is expressed as follows:
Tmin = Tf (j) (3)
It is. However, 2 ≦ j ≦ m−1.

An optical path length setting procedure in the case where the control device 20 sets the optical path length T to an arbitrary value when there is the above relationship will be described below.
First, in step 500, the control device 20 adjusts the optical path length T to be set, the minimum fixed delay amount Tf (j) of the optical path length adjusting unit, and the path selection of the N × 1 optical switches 18 and 19 to be changed. By comparing the magnitude relationship with the difference between the fixed delay amounts Tf (n) (j + 1 ≦ n ≦ m) of the respective sections, the optical path length T to be set and the fixed delay difference TF (n) of the optical path length adjusting section Are compared (step S1). However,
TF (n) = Tf (n) −Tf (j) (4)
It is. However, j + 1 ≦ n ≦ m.

Subsequently, when the optical path length T to be set is smaller than the fixed delay difference TF (n) by the determination in the above step 500, the control device 20 causes the 3 × 3 optical switch group 16, 17 and N × 1 optical switches 18 and 19 are controlled.
First, the optical path length T to be set is all fixed delay differences TF (n)
0 ≦ T <TF (n) (5)
In the case of, from Equation (2) and Equation (3),
T <TF (n) = Tf (n) −Tf (j)
T ≦ Tv (j) = l ₀ (2 ^j−1 −1) (6)
It becomes. Therefore, the required number j of optical switches is calculated by equation (6) (step S21), the inputs of the N × 1 optical switches 18 and 19 are set to i (step S22), and the optical path length T to be set is set to the jth Setting is performed using the 3 × 3 optical switches 16j and 17j (step S23). Here, l ₀ is the unit optical path length, 2 ≦ j ≦ m−1. Therefore, the output from the jth 3 × 3 optical switches 16j and 17j is selected as the input of the N × 1 optical switches 18 and 19, and the set optical path length T (j to the jth 3 × 3 optical switches 16j and 17j is selected. )
T (j) = T (7)
And

On the other hand, when the optical path length T desired to be set by the determination in step 500 is equal to or larger than the fixed delay difference TF (n), the control device 20 performs 3 × 3 optical switch groups 16, 17 and N as follows in step 502. X1 Controls optical switches 18 and 19.
First, assuming that the largest fixed delay difference TF (n) among the fixed delay differences TF (n) smaller than the optical path length T to be set is the kth fixed delay difference TF (k), the N × 1 optical switch 18, The output of the k th 3 × 3 optical switch 16k, 17k is selected as the input of 19 (step S31).

Next, the set optical path length Tv obtained by subtracting the fixed delay difference TF (k) from the optical path length T to be set is calculated as the set optical path length T (k) to the kth 3 × 3 optical switches 16k and 17k ( Step S32), each optical switch is set (Step S33). However,
Tv = T-TF (k) (8)
It is. The set optical path length T (k) to the kth 3 × 3 optical switches 16k and 17k is
T (k) = Tv (9)
It is.

As described above, in the control device 20, the optical path length is set to an arbitrary length by the process 500, the process 501 and the process 502.
Here, the minimum optical path length Tmin, the maximum optical path length Tmax, and the variable optical path length Tver of the discrete optical path length adjustment unit in this embodiment are m 3 × 3 optical switches 16m, in which one system of the discrete optical path length adjustment unit is m. If it is composed of 17m,
Tmin = Tf (j)
Tmax = Tf (m) + Tv (m)
Tver = Tmax -Tmin
= Tf (m) -Tf (j) + Tv (m)
= TF (m) + Tv (m)
…(Ten)
It becomes.

Next, the minimum optical path length Tmin (c), the maximum optical path length Tmax (c) and the variable optical path length Tver (c) of the optical path length adjustment unit according to the conventional method are as follows.
Tmin (c) = Tf (b)
Tmax (c) = Tf (b) + Tv (m)
Tvar (c) = Tmax (c) −Tmin (c)
= Tv (m)
… (11)
Here, assuming that the internal optical path lengths of the 2 × 2 optical switch and the 3 × 3 optical switch are equal, Tf (b) is calculated from the maximum fixed delay amount Tf (m) to the optical path length of the N × 1 optical switches 18 and 19. This is a value obtained by subtracting the optical path length from the N × 1 optical switches 18 and 19 to the selected 3 × 3 optical switches 16i and 17i.

Here, from Equation (10) and Equation (11), the difference ΔTmin in the minimum optical path length and the difference ΔTmax in the maximum optical path length between the discrete optical path length adjustment device in the present embodiment and the discrete optical path length adjustment device according to the conventional method. The variable optical path length ΔTvar is
ΔTmin = Tmin (c) -Tmin
= Tf (b) -Tf (j)
ΔTmax = Tmax (c) −Tmax
= Tf (b) -Tf (m)
ΔTmin = Tvar (c) −Tvar
= TF (m)
… (12)
It becomes.

As described above, according to the present embodiment, it is possible to decrease the minimum optical path length (minimum fixed delay) of Expression (12) by ΔTmin and increase the variable optical path length by ΔTvar.
In this embodiment, when h satisfying the formula (2) is 1 or more, the n + p-th 3 × 3 optical switches 16 (n + p) and 17 (n + p) in the range of n <n + p <n + h are set to 2 ×. A two-optical switch may be substituted.

  Further, the present embodiment can be used as an optical path length adjusting device of an uninterruptible switching system such as Non-Patent Document 2 to duplicate the working optical line. In this case, as shown in Non-Patent Document 2, first, an optical path length to be realized by the optical path length adjusting device is obtained by an optical path difference measuring unit using chirp pulse interference by test light different from communication light. . Correspondingly, the path pattern (ON / OFF pattern) of the optical switch group required to make either the system A or B as a detour that duplicates the working line is obtained. Until the pattern is actually realized, the continuity between the two systems must be cut off. For example, a port that is not connected to the 3x3 optical switch is selected as the input port to the Nx1 switch. Alternatively, a light blocking switch may be provided at the output destination of the N × 1 switch. First, in the system that is duplexed with the working line, the path pattern to be formed by the 3 × 3 optical switch group is realized by the control device that performs output selection of the 3 × 3 optical switch and output selection setting of the N × 1 optical switch. Thereafter, if the light blocking switch is switched to the ON state, the required route pattern is completed as a whole, and at the same time, the light is conducted to the route, and duplexing with the working line is achieved.

(Second Embodiment)
FIG. 4 is a block diagram showing the configuration of the second embodiment of the discrete optical path length adjusting device according to the present invention. In FIG. 4, reference numerals 31 and 32 denote wavelength-independent optical couplers (WIC) for branching the optical fiber 33 by optical fiber into an A-system optical line 34 and a B-system optical line 35, (3610, 3611, 3620, 3621,..., 36m0, 36m1), (3810, 3811, 3820, 3821,... 38m0, 38m1) have optical path lengths of 2 ⁰ , 2 ¹ , 2 ² , .., 2 ^m-1 is multiplied by the unit length l ₀ and both ends of the m optical fibers are selectively connected according to a control instruction from the control device 42. 2 × 2 port optical switches (hereinafter referred to as “2 × 2 optical switches” and collectively referred to as 2 × 2 optical switch groups 36 and 38), 371 to 37 (m−1), 391 to 39 (m-1) is a 2x2 light switch. A 1 × 2 port optical switch (hereinafter referred to as a 1 × 2 optical switch) that inputs the switch outputs of the H groups 36 and 38 and selectively outputs them according to a control instruction from the control device 42. , 40 and 41 are respectively optical switches 371 to 37 (m−1) and 391 to A and B systems according to control instructions from the control device 42. This is an N × 1 port optical switch (N is 1 to m + 1, hereinafter referred to as an N × 1 optical switch) that takes out any of 39 (m−1) selected outputs.

  That is, in the adjustment device having the above-described configuration, the pair of wavelength-independent optical couplers 31 and 32 is used to reduce the wavelength dependency of 2 × 2 port optical switch groups 36 and 38 and 1 × 2 optical switch groups 37 and 39, N. Two optical lines composed of × 1 optical switches 40 and 41 are combined as an A optical line 34 and a B optical line 35 to form a duplex optical line.

FIG. 5 shows the switching mode of the 2 × 2 optical switch. SW is a 2 × 2 optical switch, I ₁ is a first input port, and I ₂ is a second input port. In the optical switch SW, O ₁ is a first output port, and O ₂ is a second output port. As shown in FIG. 5, the 2 × 2 optical switch SW has two switching modes in which the input 2 port and the output 2 port are connected to each other in a straight or cross manner, and the internal optical path difference in the two switching modes can be ignored. Shall.

The first output port O ₁ and the (n + 1) th 2 × 2 optical switch 36 (n + 1) of the nth 2 × 2 optical switch 36 n and 38 n of each of the A system optical line 34 and the B system optical line 35, 38 (n + 1) first input port _{I 1} 2 × 2 optical path length and n-th optical fiber connects the optical switch 36n, a second output of 38n port _{O 2} and (n + 1) th 2 × 2 of The optical path lengths of the optical fibers connecting the _second input ports I2 of the optical switches 36 (n + 1) and 38 (n + 1) differ by a unit length l ₀ × 2 ^{(n + 1) / 2} . However, n is an odd number. In this configuration, the nth and n + 1 2 × 2 optical switches 36 and 38 and the n + 2 and n + 3 2 × 2 optical switches 36 and 38 are connected by 1 × 2 optical switches 37 and 39. Yes. The input / output ports of the 2 × 2 optical switches 36 and 38 not used in this configuration are non-reflective terminated. The 1 × 2 optical switches 37 and 39 of each system are connected to N × 1 optical switches 40 and 41 by optical fibers having an arbitrary length, respectively. Only the optical signals from the 1 × 2 optical switches 37 and 39 selected by the N × 1 optical switches 40 and 41 are output from the N × 1 optical switches 40 and 41.

Next, an optical path length setting method in the present embodiment will be described with reference to a control flow for the optical path length adjustment unit of the control device (42 in the present embodiment) shown in FIG. 3 together with FIG.
First, as a precondition, the maximum variable optical path length using only the optical path length difference between the 2 × 2 optical switches 36 and 38 up to the nth 1 × 2 optical switches 37 and 39 is Tv (n), and the n th The fixed delay amount obtained by adding the fixed delay amount to the 1 × 2 optical switches 37 and 39 and the fixed delay amount from the nth 1 × 2 optical switch 37 and 39 to the N × 1 optical switches 40 and 41 is expressed as Tf (n). The set optical path length to the nth 1 × 2 optical switches 37 and 39 is T (n). The magnitude relationship of the fixed delay amount Tf (n) is
Tf (n + 1) ≧ Tf (n) (13)
Suppose that However, 1 ≦ n ≦ m / 2-1 and m is the total number of 2 × 2 optical switches 36 and 38 of A system or B system. In order to continuously adjust the optical path length at unit length intervals,
Tv (n) ≧ Tf (n + h) −Tf (n) (14)
It is necessary to satisfy. However, 1 ≦ n ≦ m / 2-2. In the present invention, it is assumed that the formula (14) is satisfied.

When Expression (14) is satisfied, the input to the N × 1 optical switches 40 and 41 is from the output of the nth 1 × 2 optical switches 37 and 39 to the output of the n + hth 1 × 2 optical switches 37 and 39. Can be switched. Therefore, the minimum fixed delay amount Tmin of the optical path length adjustment unit is expressed as follows:
Tmin = Tf (j) (15)
It is. However, 1 ≦ j ≦ m / 2−2.

At this time, an optical path length setting method according to the value of the optical path length T to be set will be described below.
The optical path length T to be set, the minimum fixed delay amount Tf (j) of the optical path length adjustment unit, and the fixed delay amount Tf of each of the optical path length adjustment units that change depending on the selection of the path of the N × 1 optical switches 40 and 41. (n) In the step 500 for comparing the magnitude relationship with the difference of (j + 1 ≦ n ≦ m / 2-1), the optical path length T to be set is compared with the fixed delay difference TF (n) of the optical path length adjustment unit. However,
TF (n) = Tf (n) −Tf (j) (16)
It is. However, it is j + 1 <= n <= m / 2-1.

  When the optical path length T to be set by the determination in step 500 is smaller than the fixed delay difference TF (n), in step 501, the 1 × 2 optical switches 37 and 39 and the N × 1 optical switches 40, 41 and 2 are as follows. The x2 optical switches 36 and 38 are controlled by the control device 42.

First, the optical path length T to be set is all fixed delay differences TF (n)
0 ≦ T <TF (n) (17)
In this case, from the equations (16) and (17),
T <TF (n) = Tf (n) −Tf (j)
≦ Tv (j) = l ₀ (2 ^j −1) (18)
It becomes. Therefore, the desired optical path length T is set using the jth 1 × 2 optical switches 37 and 39. Here, l ₀ is the unit optical path length, 1 ≦ j ≦ m / 2-2. Therefore, the output from the jth 1 × 2 optical switch 37, 39 is selected as the input of the N × 1 optical switch 41-42, and the set optical path length T (j to the jth 1 × 2 optical switch 37, 39 is selected. )
T (j) = T (19)
And

  If the optical path length T to be set is equal to or larger than the fixed delay difference TF (n) by the determination in the above step 500, the above described 1 × 2 optical switches 37, 39 and N × 1 optical switch 40, 41 and 2 × 2 optical switches 36 and 38 are controlled by a control device 42.

  First, assuming that the fixed delay difference TF (n) is the largest among the fixed delay differences TF (n) smaller than the optical path length T to be set and the kth fixed delay difference TF (k) is used, the N × 1 optical switch 40 , 41, the outputs of the kth 1 × 2 optical switches 37, 39 are selected.

Next, the set optical path length Tv obtained by subtracting the fixed delay difference TF (k) from the optical path length T to be set is set as the set optical path length T (k) to the kth 1 × 2 optical switches 37 and 39. However,
Tv = T-TF (k) (20)
It is. The set optical path length T (k) to the kth 1 × 2 optical switches 37 and 39 is
T (k) = Tv (21)
It is.

As described above, the optical path length is set by steps 500 to 502 shown in FIG. Here, the minimum optical path length Tmin, the maximum optical path length Tmax, and the variable optical path length Tvar of the optical path length adjustment unit in this embodiment are configured by m 2 × 2 optical switches 36 and 38 in one system of the optical path length adjustment unit. If
Tmin = Tf (j)
Tmax = Tfb + Tv (m)
Tvar = Tmax−Tmin
= Tfb-Tf (j) + Tv (m)
…(twenty two)
It becomes. Tfb is a value obtained by adding a fixed delay from the final stage 2 × 2 optical switches 36 and 38 to a fixed delay from the final stage 2 × 2 optical switches 36 and 38 to the N × 1 optical switches 40 and 41.

Next, the minimum optical path length Tmin (c), the maximum optical path length Tmax (c), and the variable optical path length Tvar (c) of the discrete optical path length adjusting apparatus according to the conventional method are as follows.
Tmin (c) = Tf (b)
Tmax (c) = Tf (b) + Tv (m)
Tvar (c) = Tmax (c) −Tmin (c)
= Tv (m)
…(twenty three)
Tf (b) is determined from the maximum fixed delay amount Tfb to the optical path lengths of the N × 1 optical switches 40 and 41, the optical path lengths from the N × 1 optical switches 40 and 41 to the 2 × 2 optical switches 36 and 38, and all of one system. This is a value obtained by subtracting the optical path length of the 1 × 2 optical switches 37 and 39.

Here, from the equation (22) and the equation (23), the discrete optical path length adjusting device according to this embodiment and the discrete optical path length adjusting device according to the conventional method, the difference ΔTmin between the minimum optical path lengths, and the difference ΔTmax between the maximum optical path lengths. The variable optical path length ΔTvar is
ΔTmin = Tmin (c) -Tmin
= Tf (b) -Tf (j)
ΔTmax = Tmax (c) -Tmax
= Tfb-Tf (b)
ΔTmin = Tvar (c) −Tvar
= Tfb-Tf (j)
…(twenty four)
As described above, according to the present embodiment, it is possible to reduce the minimum optical path length (minimum fixed delay) of Expression (12) by ΔTmin and increase the variable optical path length by ΔTvar.

  Further, in this embodiment, when h satisfying the formula (14) is 1 or more, the n + p-th 1 × 2 optical switches 37 and 39 in the range of n <n + p <n + h are removed and the 1 × 2 light is removed. The 2 × 2 optical switches 36 and 38 connected to both ends of the switches 37 and 39 may be connected.

(Third embodiment)
FIG. 6 is a block diagram showing the configuration of the third embodiment of the discrete optical path length adjusting device according to the present invention. In FIG. 6, reference numerals 51 and 52 denote wavelength-independent optical couplers (WICs) 561 to 56 m and 581 to 58 m for bifurcating an optical fiber 53 using an optical fiber into an A-system optical line 54 and a B-system optical line 55. each a, B lineage each optical line 54 and 55, the optical path length is 2 ^0, 2 ^1, 2 ^2, ..., is given by multiplying the unit length l ₀ a power of 2, represented by 2 ^m-1 A 2 × 2 port optical switch (hereinafter referred to as a 2 × 2 optical switch) having a small wavelength dependency, which selectively connects both ends of the m optical fibers according to a control instruction from the control device 62. 2 × 2 optical switch groups 56 and 58 are collectively referred to), 571 to 57 (m−1) and 591 to 59 (m−1) input switch outputs of the 2 × 2 optical switch groups 56 and 58. 1 × 2 ports that are selectively output in response to control instructions from the control device 62. Optical switches (hereinafter referred to as 1 × 2 optical switches, and collectively referred to as 1 × 2 optical switch groups 57 and 59), 60 and 61, respectively, according to control instructions from the control device 62, A, An N × 1 port optical switch (N is 1 to m + 1, hereinafter, N × 1) for extracting one of the selected outputs of the optical switches 571 to 57 (m−1) and 591 to 59 (m−1) of each of the B systems. It is written as an optical switch).

  That is, in the adjusting device having the above-described configuration, the pair of wavelength-independent optical couplers 51 and 52 is used to reduce the wavelength dependency of the 2 × 2 port optical switch groups 56 and 58 and the 1 × 2 optical switch groups 57 and 59, N. Two optical lines composed of × 1 optical switches 60 and 61 are coupled as an A-system optical line 54 and a B-system optical line 55 to form a duplex optical line.

FIG. 7 shows the switching mode of the 2 × 2 optical switch. SW is a 2 × 2 optical switch, I ₁ is a first input port, I ₂ is a second input port, O ₁ is a first output port, and O ₂ is a second output port. As shown in FIG. 7, the 2 × 2 optical switch SW has two switching modes in which the input 2 port and the output 2 port are connected to each other in a straight or cross manner, and the internal optical path difference in the two switching modes is ignored. It shall be possible.

N-th of the 2 × 2 optical switch 56n of each system of system A 54 and system B 55, 58n is the switching mode light input from the first input port I ₁ is output from the first output port O ₁ The light input from the second input port I ₂ after the light input from the straight light path and the first input port I ₁ is output from the second output port O ₂ is the first output port O _1. Are connected by waveguides (optical fibers) so that the optical path lengths of the optical paths with the switching mode output from are different by the unit length l ₀ × 2 ⁿ⁻¹ . The n-th 2 × 2 optical switch and the (n + 1) th 2 × 2 optical switch of each system are the first output port O ₁ of the n-th 2 × 2 optical switch and the first of the n + 1-th 2 × 2 optical switch. The input port I ₁ is connected by 1 × 2 optical switches 57 and 59. The 1 × 2 optical switches 57 and 59 of each system are connected to the N × 1 optical switches 60 and 61 by optical fibers having an arbitrary length, respectively. Only the optical signals from the 1 × 2 optical switches 57 and 59 selected by the N × 1 optical switches 60 and 61 are output from the N × 1 optical switches 60 and 61.

Next, an optical path length setting method in the present embodiment will be described with reference to a control flow for the optical path length adjustment unit of the control apparatus (62 in the present embodiment) shown in FIG.
First, as a precondition, the maximum variable optical path length using only the optical path length difference between the 2 × 2 optical switches 56 and 58 up to the nth 1 × 2 optical switches 57n and 59n is Tv (n), and the nth A fixed delay amount obtained by combining a fixed delay amount from the 1 × 2 optical switches 57n and 59n and a fixed delay from the nth 1 × 2 optical switch 57n and 59n to the N × 1 optical switches 60 and 61 is represented by Tf (n), The set optical path length to the nth 1 × 2 optical switches 57n and 59n is T (n). The magnitude relationship of the fixed delay Tf (n) is
Tf (n + 1) ≧ Tf (n) (25)
Suppose that However, 1 ≦ n ≦ m−2 and m are the total number of the 2 × 2 optical switches 56 and 58 of the A system or the B system.

In order to continuously adjust the optical path length at unit length intervals,
Tv (n) ≧ Tf (n + h) −Tf (n) (26)
It is necessary to satisfy. However, 1 ≦ n ≦ m−2.
In the present embodiment, it is assumed that Expression (26) is satisfied. When Expression (26) is satisfied, the input to the N × 1 optical switches 60 and 61 is the n + hth 1 × 2 optical switch 57 (n + h), 59 from the output of the nth 1 × 2 optical switch 57n and 59n. The output is switched to (n + h). Therefore, the minimum fixed delay amount Tmin for the discrete optical path length adjustment is expressed as follows:
Tmin = Tf (j) (27)
It is. However, 1 ≦ j ≦ m−1. At this time, an optical path length setting method according to the value of the optical path length T to be set will be described below.

The optical path length T to be set, the minimum fixed delay amount Tf (j) of the optical path length adjustment unit, and the fixed delay Tf () of each of the optical path length adjustment units that change depending on the selection of the path of the N × 1 optical switches 60 and 61. n) In the step 500 of comparing the magnitude relationship with the difference of (j + 1 ≦ n ≦ m−1), the optical path length T to be set is compared with the fixed delay difference TF (n) of the optical path length adjustment unit. However,
TF (n) = Tf (n) −Tf (j) (28)
It is. However, it is j + 1 <= n <= m-1.

  If the optical path length T to be set is smaller than the fixed delay difference TF (n) as determined in the above step 500, the 1 × 2 optical switches 57 and 59 and the N × 1 optical switch 60, 61 and 2 × 2 optical switches 56 and 58 are controlled by a control device 62.

First, the optical path length T to be set is all fixed delay differences TF (n)
0 ≦ T <TF (n) (29)
In the case of, from Equation (28) and Equation (29)
T <TF (n) = Tf (n) −Tf (j)
≦ Tv (j) = l ₀ (2 ^j −1) (30)
It becomes. Accordingly, the optical path length T to be set is set using the jth 1 × 2 optical switches 57j and 59j. Here, l ₀ is a unit optical path length, 1 ≦ j ≦ m−1. Therefore, the output of the jth 1 × 2 optical switch 57j, 59j is selected as the input of the N × 1 optical switch 60, 61, and the set optical path length T (j to the jth 1 × 2 optical switch 57j, 59j is selected. )
T (j) = T (31)
And

  If it is determined in step 500 that the optical path length T to be set is equal to or larger than the fixed delay difference TF (n), in step 502, the 1 × 2 optical switches 57 and 59 and the N × 1 optical switches 60 and 61 and The 2 × 2 optical switches 56 and 58 are controlled by the control device 62.

  First, assuming that the largest fixed delay difference TF (n) among the fixed delay differences TF (n) smaller than the optical path length T to be set is the kth fixed delay difference TF (k), the N × 1 optical switch 60, As the input of 61, the output of the kth 1 × 2 optical switch 57k, 59k is selected.

Next, the set optical path length Tv obtained by subtracting the fixed delay difference TF (k) from the optical path length T to be set is set as the set optical path length T (k) to the kth 1 × 2 optical switches 57k and 59k. However,
Tv = T−TF (k) (32)
It is. The set optical path length T (k) to the kth 1 × 2 optical switches 57k and 59k is
T (k) = Tv (33)
It is.

As described above, the optical path length is set by Step 500, Step 501, and Step 502 shown in FIG.
Here, the minimum optical path length Tmin, the maximum optical path length Tmax, and the variable optical path length Tvar of the discrete optical path length adjusting device in the present embodiment are m 2 × 2 optical switches 56 and 58 in one system of the optical path length adjusting unit. If configured,
Tmin = Tf (j)
Tmin = Tfb '+ Tv (m)
Tvar = Tmax−Tmin
= Tfb'-Tf (j) + Tv (m)
… (34)
It becomes.

Tfb ′ is a value obtained by combining a fixed delay amount from the last stage 2 × 2 optical switches 56 and 58 to a fixed delay amount from the last stage 2 × 2 optical switches 56 and 58 to the N × 1 optical switches 60 and 61. It is.
Next, the minimum optical path length Tmin (c), the maximum optical path length Tmax (c), and the variable optical path length Tvar (c) of the discrete optical path length adjusting apparatus according to the conventional method are as follows.
Tmin (c) = Tf (b)
Tmax (c) = Tf (b) + Tv (m)
Tvar (c) = Tmax (c) −Tmin (c)
= Tv (m)
… (35)
Tf (b) is equal to the optical path length of the N × 1 optical switches 60 and 61 from the maximum fixed delay amount Tfb ′ and the optical path length from the N × 1 optical switches 60 and 61 to the 2 × 2 optical switches 56 and 58 in the final stage. This is a value obtained by subtracting the optical path lengths of the 1 × 2 optical switches 57 and 59 of all the systems.

Here, from Expression (34) and Expression (35), the difference ΔTmin in the minimum optical path length and the difference ΔTmax in the maximum optical path length between the discrete optical path length adjustment apparatus in the present embodiment and the discrete optical path length adjustment apparatus according to the conventional method. The variable optical path length ΔTvar is
ΔTmin = Tmin (c) -Tmin
= Tf (b) -Tf (j)
ΔTmax = Tmax (c) −Tmax
= Tfb'-Tf (b)
ΔTmin = Tvar (c) −Tvar
= Tfb'-Tf (j)
… (36)
As described above, according to the present embodiment, it is possible to decrease the minimum optical path length (minimum fixed delay amount) of Expression (36) by ΔTmin and increase the variable optical path length by ΔTvar.

  In this embodiment, when h satisfying the equation (26) is 1 or more, the n + p-th 1 × 2 optical switches 57 and 59 in the range of n <n + p <n + h are removed and the 1 × 2 light is removed. The 2 × 2 optical switches 56 and 58 connected to both ends of the switches 57 and 59 may be connected to each other.

(Fourth embodiment)
FIG. 8 is a block diagram showing the configuration of the fourth embodiment of the discrete optical path length adjusting device according to the present invention. In FIG. 8, reference numerals 71 and 72 denote wavelength-independent optical couplers (WICs) for splitting an optical line 73 formed of an optical fiber into an A-system optical line 74 and a B-system optical line 75, 761 to 76m, 781 to 78m. each a, B lineage each optical line 74 and 75, the optical path length is 2 ^0, 2 ^1, 2 ^2, ..., is given by multiplying the unit length l ₀ a power of 2, represented by 2 ^m-1 A 2 × 2 port optical switch (hereinafter referred to as a 2 × 2 optical switch) having a small wavelength dependency, which selectively connects both ends of the m optical fibers according to a control instruction from the control device 82. 2 × 2 optical switch groups 76 and 78 are collectively referred to), 771 to 77 (m−1) and 791 to 79 (m−1) input the switch outputs of the 2 × 2 optical switch groups 76 and 78. 1 × 2 ports that are selectively output in response to control instructions from the control device 82. Optical switches (hereinafter referred to as 1 × 2 optical switches, and collectively referred to as 1 × 2 optical switch groups 77 and 79), 80 and 81, respectively, according to control instructions from the control device 82, A, An N × 1 port optical switch (N is 1 to m + 1, hereinafter N × 1) for extracting one of the selected outputs of the optical switches 771 to 77 (m−1) and 791 to 79 (m−1) of each of the B systems. It is written as an optical switch).

  That is, in the adjustment device having the above-described configuration, the pair of wavelength-independent optical couplers 71 and 72 is used to reduce the wavelength dependency of 2 × 2 port optical switch groups 76 and 78 and 1 × 2 optical switch groups 77 and 79, N. Two optical lines composed of × 1 optical switches 80 and 81 are combined as an A optical line 74 and a B optical line 75 to form a duplex optical line.

As described with reference to FIG. 5, the switching mode of the 2 × 2 optical switch has two switching modes in which the input 2 port and the output 2 port are connected in a straight or cross manner, and the internal optical path difference in the two switching modes is ignored. It shall be possible.
N-th of the 2 × 2 optical switch 76n of each system of system A 74 and system B 75, a first output port _{O 1} and (n + 1) th of the 2 × 2 optical switch 76 of 78n (n + 1), 78 of (n + 1) first input optical path length of the port _{I 1} and the optical fiber which connects the n-th of the 2 × 2 optical switch 76n, a second output port _{O 2} and 1 × 2 optical switches 77 and 79 and the n + 1 th 78n of the 2 × 2 optical switch 76 (n + 1), the optical path length of 78 (n + 1) of the second input port I ₂ connects the in which the light path is different by a unit length l ₀ × 2 ^n-1. The input / output ports of the 2 × 2 optical switches 76 and 78 not used in this configuration are non-reflective terminated.

  The 1 × 2 optical switches 77 and 79 of each system are connected to N × 1 optical switches 80 and 81 by optical fibers having an arbitrary length, respectively. Only the optical signals from the 1 × 2 optical switches 77 and 79 selected by the N × 1 optical switches 80 and 81 are output from the N × 1 optical switches 80 and 81.

Next, an optical path length setting method in the present embodiment will be described with reference to a control flow for the optical path length adjustment unit of the control device (82 in the present embodiment) shown in FIG. 3 together with FIG.
First, as a precondition, the maximum variable optical path length using only the optical path length difference between the 2 × 2 optical switches 76 and 78 up to the nth 1 × 2 optical switches 77 and 79 is Tv (n), and the n th The fixed delay amount obtained by adding the fixed delay amount to the 1 × 2 optical switches 77 and 79 and the fixed delay amounts from the nth 1 × 2 optical switch 77 and 79 to the N × 1 optical switches 80 and 81 is expressed as Tf (n ), The set optical path length to the nth 1 × 2 optical switches 77 and 79 is T (n). The magnitude relationship of the fixed delay Tf (n) is
Tf (n + 1) ≧ Tf (n) (37)
Suppose that However, 1 ≦ n ≦ m−2 and m are the total number of 2 × 2 optical switches 76 and 78 of A system or B system.

In order to continuously adjust the optical path length at unit length intervals,
Tv (n) ≧ Tf (n + h) −Tf (n) (38)
It is necessary to satisfy. However, 2 ≦ n ≦ m−2.
In the present embodiment, it is assumed that Expression (38) is satisfied. When Expression (38) is satisfied, the input to the N × 1 optical switches 80 and 81 is from the output from the nth 1 × 2 optical switches 77 and 79 from the n + hth 1 × 2 optical switches 77 and 79. Switch to output. Therefore, the minimum fixed delay amount Tmin of the optical path length adjustment unit is defined as follows.
Tmin = Tf (j) (39)
It is. However, 2 ≦ j ≦ m−2.

At this time, an optical path length setting method according to the value of the optical path length T to be set will be described below.
The optical path length T to be set, the minimum fixed delay amount Tf (j) of the optical path length adjustment unit, and the fixed delay amount Tf of each of the optical path length adjustment units that change depending on the selection of the path of the N × 1 optical switches 80 and 81. (n) In the step 500 for comparing the magnitude relationship with the difference of (j + 1 ≦ n ≦ m−1), the optical path length T to be set is compared with the fixed delay difference TF (n) of the optical path length adjustment unit. However,
TF (n) = Tf (n) −Tf (j) (40)
It is. Further, j + 1 ≦ n ≦ m−1.

  If it is determined in step 500 that the optical path length T to be set is smaller than the fixed delay difference TF (n), in step 501, 1 × 2 optical switches 77 and 79 and N × 1 optical switches 80 and 81 and The 2 × 2 optical switches 76 and 78 are controlled by the control device 82.

First, the optical path length T to be set is all fixed delay differences TF (n)
0 ≦ T <TF (n) (41)
In this case, from the equations (40) and (41),
T <TF (n) = Tf (n) −Tf (j)
≦ Tv (j) = l ₀ (2 ^j−1 −1) (42)
It becomes. Therefore, the desired optical path length T is set using the jth 1 × 2 optical switches 77 and 79. Here, l ₀ is the unit optical path length, 2 ≦ j ≦ m−2. Therefore, the outputs from the jth 1 × 2 optical switches 77 and 79 are selected as inputs to the N × 1 optical switches 80 and 81, and the set optical path length T (j )
T (j) = T (43)
And

  If it is determined in step 500 that the optical path length T to be set is equal to or greater than the fixed delay difference TF (n), then in step 502, 1 × 2 optical switches 77 and 79 and N × 1 optical switches 80 and 81 and The 2 × 2 optical switches 76 and 78 are controlled by the control device 82.

  First, assuming that the largest fixed delay difference TF (n) among the fixed delay differences TF (n) smaller than the optical path length T to be set is the kth fixed delay difference TF (k), N × 1 optical switch 80 , 81, the outputs of the kth 1 × 2 optical switches 77, 79 are selected.

Next, the set optical path length Tv obtained by subtracting the fixed delay difference TF (k) from the optical path length T to be set is set as the set optical path length T (k) to the kth 1 × 2 optical switches 77 and 79. However,
Tv = T−TF (k) (44)
It is. The set optical path length T (k) to the kth 1 × 2 optical switches 77 and 79 is
T (k) = Tv (45)
It is.

As described above, the optical path length is set by the process 500, the process 501 and the process 502 shown in FIG.
Here, the minimum optical path length Tmin, the maximum optical path length Tmax, and the variable optical path length Tvar of the discrete optical path length adjusting device according to the present embodiment are m 2 × 2 optical switches 76m, If it is composed of 78m, Tmin = Tf (j)
Tmax = Tfb ″ + Tv (m)
Tvar = Tmax−Tmin
= Tfb ''-Tf (j) + Tv (m)
… (46)
It becomes.

Tfb ″ is a value obtained by adding a fixed delay amount from the last stage 2 × 2 optical switches 76 and 78 to a fixed delay amount from the last stage 2 × 2 optical switches 76 and 78 to the N × 1 optical switches 80 and 81. It is.
Next, the minimum optical path length Tmin (c), the maximum optical path length Tmax (c) and the variable optical path length Tvar (c) of the discrete optical path length adjusting apparatus according to the conventional method are as follows.
Tmin (c) = Tf (b)
Tmax (c) = Tf (b) + Tv (m)
Tvar (c) = Tmax (c) −Tmin (c)
= Tv (m)
… (47)
Here, Tf (b) is equal to the optical path length of the N × 1 optical switches 80 and 81 and the optical path length from the N × 1 optical switches 80 and 81 to the 2 × 2 optical switches 76 and 78 from the maximum fixed delay Tfb ″. This is a value obtained by subtracting the optical path lengths of the 1 × 2 optical switches 77 and 79 of all the systems.

From Equations (46) and (47), the minimum optical path length difference ΔTmin, the maximum optical path length difference ΔTmax, and the variable optical path between the discrete optical path length adjustment device in the present embodiment and the discrete optical path length adjustment device according to the conventional method. The length ΔTvar is
ΔTmin = Tmin (c) -Tmin
= Tf (b) -Tf (j)
ΔTmax = Tmax (c) −Tmax
= Tfb ''-Tf (b)
ΔTmin = Tvar (c) −Tvar
= Tfb-Tf (j)
… (48)
As described above, according to the present embodiment, it is possible to decrease the minimum optical path length (minimum fixed delay amount) of Expression (48) by ΔTmin and increase the variable optical path length by ΔTvar.

  In the present embodiment, when h satisfying the formula (38) is 1 or more, the n + p-th 1 × 2 optical switches 77 and 79 in the range of n <n + p <n + h are removed and the 1 × 2 light is removed. The 2 × 2 optical switches 76 and 78 connected to both ends of the switches 77 and 79 may be connected.

As described above, according to the present invention, it is possible to minimize the fixed delay and expand the variable optical path length range.
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. In short, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

11, 12, 31, 32, 51, 52, 71, 72 ... wavelength-independent optical coupler (WIC)
13, 33, 53, 73 ... optical line
14, 34, 54, 74 ... System A optical line
15, 35, 55, 75 ... B system optical line
16, 17 ... 3 × 3 optical switch
18, 19, 40, 41, 60, 61, 80, 81 ... N × 1 optical switch
20, 42, 62, 82 ... control device
36, 38, 56, 58, 76, 78 ... 2 × 2 optical switch
37, 39, 57, 59, 77, 79 ... 1 x 2 optical switch

Claims (2)

In a discrete optical path length adjusting device that changes the delay time of an optical signal,
A plurality of delay optical fibers whose optical path lengths are given in order by multiplying the power of 2 by the unit length;
A plurality of switching optical switch means for selectively connecting the plurality of delay optical fibers in series to generate an arbitrary delay time;
A selection light switch means for selecting and outputting an arbitrary output from the plurality of switching light switch means;
Control means for controlling switching of the plurality of switching light switch means and selection of the selection light switch means,
The plurality of switching optical switch means are 3 × 3 optical switches that selectively connect the plurality of delay optical fibers in series and use any one of the output ports as an external output port,
The selection light switch means is configured to select any output from the external output ports of each of the 3 × 3 optical switches,
The control means selectively switches the plurality of switching optical switch means in accordance with a designated delay time to serially connect the delay optical fibers, and the output of the final delay optical fiber is selectively output by the selection optical switch means. A discrete optical path length adjusting device characterized in that In a discrete optical path length adjusting device that changes the delay time of an optical signal,
A plurality of delay optical fibers whose optical path lengths are given in order by multiplying the power of 2 by the unit length;
A plurality of switching optical switch means for selectively connecting the plurality of delay optical fibers in series to generate an arbitrary delay time;
A selection light switch means for selecting and outputting an arbitrary output from the plurality of switching light switch means;
Control means for controlling switching of the plurality of switching light switch means and selection of the selection light switch means,
The plurality of delay optical fibers are selectively connected to an optical fiber that gives an offset of unit length × 1/2 length,
The control means selectively switches the plurality of switching optical switch means in accordance with a designated delay time to serially connect the delay optical fibers, and the output of the final delay optical fiber is selectively output by the selection optical switch means. A discrete optical path length adjusting device characterized in that

Images