JPS6152604A - Optical multiplexer and demultiplexer - Google Patents

Abstract

PURPOSE:To solve the difficulty for setting a parameter for further demultiplexing a wavelength of odd times exceeding three wavelengths by constituting the titled device so that a wavelength demultiplexed as a wavelength of odd times is set to <=2 wavelengths in an optical waveguide system of each stage, in a constitution for connecting in a multistage the optical waveguide system which has utilized an evanescent coupling. CONSTITUTION:Two optical waveguides 3 are connected adjacently so that an evanescent coupling is generated and interaction areas l1-l7 are constituted, and the areas l1-l4 are connected adjacently in series so as to satisfy the equation. First of all, in the area l1, wavelengths lambda4, lambda6 by which a length of the interaction area becomes odd times of a coupling length, and wavelengths lambda1, lambda2, lambda3, lambda5, lambda7, lambda8, and lambda9 by which said length becomes even times are demultiplexed, and the wavelengths of even times are made incident on the area l2. In the same way, in the area l2, the area l3, and the area l4, wavelengths lambda3, lambda7 of odd times and wavelenths lambda1, lambda2, lambda5, lambda8, and lambda9 of even times, wavelengths lambda2, lambda8 of odd times and wavelengths lambda1, lambda5, and lambda9 of even times, and wavelengths lambda1, lambda9 and a wavelength lambda5 are demultiplexed, respectively. On the other hand, the wavelengths of odd times which have been demultiplexed can be demultiplexed in the areas l5, l6, and l7, respectively. Also, in the reverse process, the multiplexing can also be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Minute Hand) The present invention relates to an optical multiplexer/demultiplexer that is configured by connecting optical wave path systems in multiple stages in which evanescent coupling occurs, and multiplexes and demultiplexes a plurality of wavelengths.

・(Prior art) A conventional optical multiplexer/demultiplexer using evanescent coupling, as described in Japanese Patent Application No. 58-88719,
It consists of a set of optical fiber pairs. With such an optical multiplexer/demultiplexer, it is possible to multiplex and demultiplex wavelengths where the length of the interaction region where evanescent coupling occurs is an odd number multiple of the coupling length determined by the strength of the evanescent coupling, and a wavelength where the length is an even number multiple.

In other words, one optical multiplexer/demultiplexer can completely multiplex and demultiplex two
wavelength, and multiple wavelengths cannot be multiplexed or demultiplexed at once. In order to multiplex and demultiplex a plurality of wavelengths, a method has been proposed in which single optical multiplexers and demultiplexers are connected in multiple stages.

Figure @6 is a multi-stage connection configuration diagram of a single optical multiplexer/demultiplexer for eight wavelengths according to the above-mentioned Japanese Patent Application No. 58-88719, where 1 is an optical multiplexer/demultiplexer and 2 is an optical fiber. Optical multiplexer/demultiplexer 1 in FIG. Thereafter, in the configuration shown in FIG. 1, wavelengths are sequentially demultiplexed by optical multiplexers/demultiplexers 1(b) to 1(2).

(rjIa point to be solved by the present invention) However, in order to further demultiplex 8 or more wavelengths that have been demultiplexed as 1 odd-numbered wavelengths, the length of the interaction region of the optical multiplexer/demultiplexer and the spacing between the optical waveguides must be adjusted. However, changing the optical waveguide spacing changes the wavelength characteristics of the coupling length. For example, for two of the three wavelengths, the length of the interaction region becomes an even or odd multiple of the coupling length. Parameters can be set, but at this time, generally for the remaining wavelength, the length of the interaction region is no longer just an integer multiple of the coupling length. Wavelength λ2.λ, which is demultiplexed as an odd-numbered wavelength.

λ6. λ8 is further multiplied by an even number, λ3. λ6 and an odd multiple of wavelength λ6. Optical multiplexing/demultiplexing 1i for complete demultiplexing into λ8
1 (There is a problem that parameter setting of C1 is difficult and leads to crosstalk deterioration.

(Means for Solving the Problems) The present invention provides an optical multiplexer/demultiplexer for multiple wavelengths by connecting optical waveguide systems in which evanescent coupling occurs in multiple stages. The length of the interaction region and the demultiplexing wavelength sequence in each optical waveguide system are set so that the number of wavelengths demultiplexed is two or less. The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a conceptual diagram showing the optical waveguide configuration and demultiplexing process of an optical multiplexer/demultiplexer according to the present invention, and 3 is an optical waveguide.

In Figure 1, □, 1. , 1. , 1. .

1. In the regions 16 and 1, the two optical waveguides are in contact with 1I4 so that evanescent coupling occurs,
It constitutes an interaction area. The optical waveguide spacing is the same, and the length of the interaction region satisfies the following formula l□* 12.
1. The interaction regions of and l are arranged adjacent to each other in series.

tl-21, -4t8-814 (1) Since the optical waveguide configuration shown in FIG. ,λ. is demultiplexed in the process described below.

t, m s(m-1)zo(λ1) = a(m+1
)to(λ,)(junt, -4+2m-1)jo(λ
, ) −4(2m+1)jo(λ8) (8
)t, -2+4m-1) jotλ3) -2+4m+
1) tofλ, ) +41t, -(sm-i)1
0(λ,) −[8m+1)to(λ6) (
51tx-amtc(λ, )
+6 madashi t. (λi) (1””1
*2+...19) is the coupling length of wavelength λ1, and m is an arbitrary natural number. First, in the region of t□, the equation (gradient ~ (6
), the length of the interaction region is an odd number multiple of the bond length. λ, and the wavelength λ0. which is an even number multiple. λ3. λ8. λ5
．． λ7. λ8. λ is demultiplexed, and even-numbered wavelengths are incident on the interaction region 13 of the next stage. Next l! In the region of wavelength λ8. from equations (1) and (4). λ, the length of the interaction region E is an odd number multiple of the bond length, and from equations (1) to (3) and equation (6), the wavelength λ0. S21λ5.
λ6. For λ, the length of the interaction region is an even multiple of the bond length. Therefore, in the area of /2, the odd number times the wavelength is 231λ7, and the even number times the wavelength λ0. λ8. λ5. λ
8Iλ is demultiplexed, and the wavelengths of even multiples are incident on the next stage interaction region t8. Furthermore, expression + 1) ~ (Shun and expression (
Similarly, from the relationship 6), l.

In the region of wavelength λ3. Wavelength λI that is an even number multiple of λ8
Iλ5. λ, is demultiplexed, ! In the region of , the wavelength λ□.

λ and wavelength λ are separated. Depending on whether the natural number m in equations (2] to (6) is even or odd, the wavelength in the region t is 1.λ.
.

Even and odd multiples of the wavelength λ and wavelength λ are switched.

@1 Figure shows the case where m is an even number, and the wavelength λ0. λ
, is an odd number multiple wavelength and one wavelength λ5 is an even number multiple wavelength. on the other hand,
Odd times wave 1 in the region l, t and t
! Three sets λ consisting of two wavelengths separated as long wavelengths, and λ6゜λ
, and λ7 and λ2 and 28 are each 1. , 1. and 1
By appropriately setting the distance between the optical waveguides and the length of the interaction region in the region 7, demultiplexing can be easily performed.

Furthermore, the optical waveguide configuration shown in FIG. 1 also allows the multiplexing function to be realized by reverse polarization. The optical waveguide configuration shown in FIG.
It can be applied as an optical multiplexer/demultiplexer for eight wavelengths of r'B *..., λ,). Since the number of wavelengths that are separated as odd multiples in one stage of interaction region is less than two wavelengths, optical multiplexing and demultiplexing to separate odd multiples of wavelengths is a problem in the 6゛η configuration shown in Figure 6. Device parameters can be easily set.

The optical waveguide configuration shown in Figure 1 is an 8-wavelength Iil configuration in which four stages of interaction regions are connected in which the length of the interaction region is half the length of the previous stage. By connecting N stages, an optical multiplexer/demultiplexer for 2N wavelengths can be constructed. The demultiplexed wavelength series at this time is a wavelength that satisfies the condition of the following equation.

FIG. 2 is a diagram showing a multistage connection configuration of an optical multiplexer/demultiplexer showing a first embodiment of the present invention. In FIG. 2, 1 is an optical multiplexer/demultiplexer, and 2 is an optical fiber. The configuration shown in FIG. 2 uses an optical multiplexer/demultiplexer that utilizes evanescent coupling, which is composed of a pair of optical fibers as the optical waveguide system in which evanescent coupling occurs in FIG. 1. ．． (al SL (t)
l, 1(C), 1 (d) % 1 (el, 1(g)
and 1) are interaction areas 1111 and 1111 in FIG. 1, respectively.
, 1. +1. , 1. , 16 and 17. In this configuration, the ratio of the distance between the core centers to the core diameter ((i/a)) and the length l of the interaction region in each optical multiplexer/demultiplexer are set to the values shown in Table 1 as an example.

Table 1 Optical multiplexer/demultiplexer 64 construction parameters and optical fiber specifications are core diameter 2a - No' (μm
], refractive index n -1,46, relative refractive index difference Δ-0,2 (%
] 1.

At this time, when the 8 wavelengths shown in Table 2 are input to the optical multiplexer/demultiplexer 1 (aJ in Fig. 2), each wavelength is demultiplexed by the wavelength shown in Fig. 2, and crosstalk at each wavelength occurs. is calculated for a OdB i degree and the parameters in Table 1 as shown in Table 2.

Table 2 Demultiplexing wavelength and crosstalk The wavelength series shown in Table 2 is m in equations (2) to (6).
- This is the case of a. In this manner, an optical multiplexer/demultiplexer for eight wavelengths can be realized with the configuration shown in FIG.

FIG. 3 is a configuration diagram of an optical multiplexer/demultiplexer showing a second embodiment of the present invention. In FIG. 3, 4 is a grooved substrate, 5 is a thin fiber, and 6 is a holding substrate. In Fig. 3, the grooved substrate is made by providing grooves in a material substrate having the same refractive index as the cladding of the optical fiber.) The small diameter fiber 5 is obtained by drawing an optical fiber into a thin line, t, f, and the like. This is with some of the cladding removed. By positioning the small diameter fibers 6 along the groove pattern prepared on the grooved substrate 4, the small diameter fibers 6 are arranged in "mutually adjacent regions ti(i
-1+21..., 7), and become the optical fiber Clara.

It is fixed with a holding substrate 6 made of a material having the same refractive index as .

FIG. 3 shows an integrated optical waveguide configuration shown in FIG. 7
) constitutes an interaction region where evanescent coupling occurs. By providing a curvature R or the like on one or both of the two small-diameter fibers and separating the two optical waveguides, a region where evanescent coupling occurs and a region where it does not occur are connected. With such a configuration as shown in FIG. 3, eight wavelengths can be multiplexed and demultiplexed as explained using FIG. 1, and an optical multiplexer/demultiplexer for eight wavelengths can be realized.

The fourth factor is a configuration diagram of an optical multiplexer/demultiplexer showing a third embodiment of the present invention. Nail 4 In the diagram, 1 is an optical multiplexer/demultiplexer, 4 is a grooved board,
5 is a small diameter fiber, and 6 is a holding substrate. FIG. 4 shows the evanescent couplings 1, , 1. in FIG. 3.
, 1. This is an optical multiplexer/demultiplexer configured except for the regions t7 and t7. As explained using FIG. 1, an optical waveguide system consisting of a small diameter fiber 5 on a grooved substrate 4 allows the λ0, λ2, . . .
・, λ8 can be split into two wavelengths at each end of the small diameter fiber 5, (λ and λ8 at the bJ end, and λ8 and 22% at the al end).
(λ2 and λ8 are demultiplexed at the (al end), and λ1 and λ6 are demultiplexed at the (e) end. Combining can also be performed in the reverse process.

By connecting the optical multiplexer/demultiplexer 1 to each end of (C1, (d) and (61), the wavelengths λ, 8, λ and λ7, λ2 and λ8, and λ and λ are demultiplexed. In this way, the optical multiplexer/demultiplexer shown in Figure 4 can separate eight wavelengths into two wavelengths each.Therefore, as shown in Figure 4, wavelengths λ0, λ2, λ3°, λ, and wavelengths)6. Using λ6, λ2, and λ8 in the up and down reverse directions, the narrow diameter 7 eye t< 6 (7) (b) r (
Optical multiplexer/demultiplexer 1 at each end of cl r (dl and (e)
If used by connecting, for example, it can be applied as a signal distributor to each terminal in a wavelength division multiplexing system that assigns two upstream and downstream wavelengths to one terminal. FIG. 6 is a perspective view of an optical multiplexer/demultiplexer showing an embodiment of
(b) 8 is an optical waveguide, and 7 is a dielectric substrate. 6th
Figure (4.

(b) The medium optical waveguide 3 is manufactured by partially increasing the refractive index of the dielectric substrate 7. FIG. 5 (aJ is the one in which the optical waveguide system of the optical multiplexer/demultiplexer shown in FIG. It can be applied as an optical multiplexer/demultiplexer for use.Furthermore, it is fabricated as an optical waveguide pattern on a dielectric substrate (bl is the optical waveguide system of the optical multiplexer/demultiplexer shown in No. 4FgJ). As explained using
For example, it can be applied as a signal distributor to each terminal in a wavelength multiplexing system that assigns two upstream and downstream wavelengths to one terminal.

(Effects of the Invention) As explained above, in the optical multiplexer/demultiplexer according to the present invention, in a configuration in which optical waveguide systems using evanescent coupling are connected in multiple stages, each stage of the optical waveguide system demultiplexes the wavelength as an odd number multiple. Since this is a configuration in which the number of wavelengths is reduced to two or less, there is an advantage that the difficulty in setting parameters for further demultiplexing wavelengths that are odd multiples of three or more than one wavelength, which was a problem in the conventional configuration, can be solved.

[Brief explanation of the drawing]

1 is a conceptual diagram of the optical waveguide configuration and demultiplexing of the optical multiplexer/demultiplexer according to the present invention; FIG. 2 is a multistage connection configuration diagram of the optical multiplexer/demultiplexer showing the first embodiment of the present invention; The figure is a block diagram of an optical multiplexer/demultiplexer showing a second embodiment of the present invention, Figure 4 is a block diagram of an optical multiplexer/demultiplexer showing a third embodiment of the present invention, Figures 5(a) and ( bJ is a perspective view of an optical multiplexer/demultiplexer showing the fourth and fifth embodiments of the present invention, respectively, and FIG. 6 is a multistage connection configuration diagram of a conventional purchased optical multiplexer/demultiplexer. ]ibl+ C++ 1(d)+
He1r 1(f)+1@) ”・Optical multiplexer/demultiplexer 2・・
- Optical fiber 3... Optical waveguide 4... Grooved substrate 5... Small diameter fiber 6... Holding substrate 7... Dielectric substrate λ□, λ, l, λ8. λ6
．． λ5. of. , λ7. λ8. λ. ... Wavelength 1, . 1.
l, et al'41'517151/7...interaction region. Patent Applicant Nippon Telegraph and Telephone Public Corporation Figure 1 Figure 2
f), /<))-=l14H wave82...χ Buai l
C Figure 5 (a) (b) l (Laren

Claims (1)

[Claims] 1. A system consisting of two optical waveguides adjacent to each other at a certain distance is arranged in multiple stages in series so that evanescent coupling occurs, and one of the two optical waveguides is A light combining system having a structure that extends through the system at each stage, and characterized in that the length of the interaction region where evanescent coupling occurs in the system at each stage is half the length of the interaction region in the system at the previous stage. Wave equipment. 2. Claim 1, characterized in that the output side of the optical waveguide that is not lead-through in the system at each stage is connected to one optical waveguide of a system consisting of two optical waveguides in which evanescent coupling occurs. Optical multiplexer/demultiplexer described in section. 3. An optical multiplexer/demultiplexer according to claim 1 or 2, characterized in that a system consisting of two adjacent optical waveguides in which evanescent coupling occurs is constructed by placing the cores of optical fibers adjacent to each other. 4. As a system consisting of two adjacent optical waveguides in which evanescent coupling occurs, an optical multiplexer/demultiplexer is used, which consists of two optical fibers with their cladding partially removed and their cores placed adjacent to each other. An optical multiplexer/demultiplexer according to claim 1 or 2, characterized in that the optical multiplexer/demultiplexer is constructed by connecting multiple wavers in multiple stages. 5. A patent characterized in that an optical fiber with a portion of the cladding removed is arranged in a groove provided on a substrate having the same refractive index as the cladding of the optical fiber, thereby being integrated onto a single substrate. An optical multiplexer/demultiplexer according to claim 3. 6. The optical multiplexer/demultiplexer according to claim 1 or 2, characterized in that it is constructed by fabricating an optical waveguide on a dielectric substrate.