DE8128658U1 - DIRECTIONAL COUPLER FOR OPTICAL SIGNALS - Google Patents

Description

Bktatunegbgpplgr used as a switch for optical signals

The invention "relates to a special switch for optical signals in integrated technology, especially for a switching network with purely optical intermediate lines in a telephone switching system. In addition, however, the invention is also suitable for other cases in which light is to be switched in a light guide.

The invention is based on a special directional coupler, compare the preamble of the patent claim 1, which for example by Electronics Letters 12 (October 28, 1976) No 22, 575 - 577, in particular Fig. 2 on page 576, as well as Appl. Phys. Lett. 28 (May I, 1976) No. 9, 503 - 506, especially Fig. 1 (a) on page 504, is previously known. These known directional couplers are although in each case along the coupling path of one of the two light guides, the first light guide, one behind the other two separately controllable electrodes attached, but only a single one on the other, second light guide, very long electrode, in such a way that each of the two electrodes on the first light guide opposite the single electrode of the second light guide, based on the longitudinal direction of the coupling path.

These known directional couplers already require significantly less control voltage between the electrodes,

Be 1 KeI / 9/28/81

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ταπί reliably this directional coupler serving as a switch to be switched through either directly or crosswise, compared to the "known directional couplers" which only a single electrode is attached to each light guide per coupling path.

The object of the invention is to be able to further reduce the control voltage between the electrodes of the directional coupler considerably.
10

This object of the invention is achieved by the measure mentioned in character C of claim 1.

The additional measure mentioned in protection claim 2 g allowed to further reduce the relevant control voltage or the relevant control voltages considerably to be able to.

The invention is explained in more detail with reference to the two figures.

Figure 1 shows a particularly simple example of the invention with two electrodes along each light guide f χ within the coupling path. In the example shown in FIG. 2, electrodes per light guide are attached within the same coupling path.

In both figures, there is in each case a directional coupler serving as a switch for optical ones

30 signals in integrated technology. They are each closely adjacent, e.g. at a distance of 3 ^, along the coupling path two parallel light guides A-A ', B-B' mounted on a substrate. The substrate can be, for example, LiNbO, which can be obtained, for example, by means of Ti

35 was doped in order to produce the light guides in the substrate.

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In principle, however, the invention is not limited to a substrate made of this material because the physical effect on which the measure specified in the indicator of protection claim 1 is based, can in principle also be achieved with substrates made of other materials.

Both figures are examples in which electrically controllable, electrically conductive electrodes Ei i .. E22 or 111 ·. E24 are attached. Depending on the electrical control voltage, compare V1 / V2, between the individual electrodes, these electrodes allow the light supplied in one or both light guides to be passed on directly or exchanged crosswise between the light guides. In the case of direct transmission, the light supplied at A is ^{carried away via the first light guide at A 1} and the light supplied via B to the second light guide is carried away at B. In the case of crosswise reversed forwarding, on the other hand, the light fed to the first light guide at A is ^{discharged via the second light guide at B 1} and the light fed to the second light guide at B is discharged via ( A ¹ , i.e. via the first light guide. By the way, such switches are also for electrical instead of optical signals has long been known, in particular in connection with the formation of complicated switching networks in telephone switching systems, compare DE-AS 20 36 176 and 20 36 128, as well as US Pat. No. 3,593,295 and 3,638,193.

30th

In the illustrated example of implementation of the invention are on both light guides along the coupling path, and not just on one of them, at least two electrodes attached one behind the other. These electrodes are attached in a special way so that that namely one electrode at a time, compare

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E11, on the first light guide AA ¹ opposite an electrode, compare E21, is located on the second light guide BB '. In addition, the two electrodes, each opposite one another, compare E11 / E21 and E12 / E22, can be controlled separately. These opposing electrodes, compare Ε1Ϊ / Ε21, thus each form a pair of electrodes in which each of the two electrodes is controlled by a different potential of the control voltage V1 / V2. Note in particular in the figures that the electrode E11 is controlled by the potential V1, but the electrode E21 opposite is controlled by the potential V2 of this control voltage.

Despite this high number of electrodes in the invention - namely, it contains at least 4 electrodes per coupling path, it is not necessary, however, to have at least cb >> i different potentials to control the switch

As to be used in the prior art, V It was found that for control purposes it is sufficient as a switch that each electrode, compare E11, on the first light guide AA 'is electrically conductive with an electrode belonging to a different pair of electrodes, compare E22 , is connected to the second light guide B-3 ^1. In the examples shown in both figures, the simplest case is "only two different potentials, compare V1 and V2, necessary to control all electrodes due to such cross-wise conductive connections between the electrodes", with insulating layers Is Prevent short circuits between ΊΛ / 12 « Because with the invention not only on one light guide,

j5o but several of their own on each of the two light guides Electrodes are attached which, viewed in the longitudinal direction of the coupling path, alternately one behind the other can be controlled with different potentials, is the level of the control voltage V1 / V2, which is used for switching

35 are necessary in both switching states, clearly in each case smaller than if only a single, very long electrode had been attached to one of the two light guides.

- 5 - VPA g) ρ 6 2 81) DE f It was also shown that the influence on the speed of light of the light rays in
the two light guides along this coupling path, respectively
The more electrodes in a row, the more intense it is

act on each of the two light guides, especially low
The levels of the control voltage are, see Fig. 2,
achievable if more than just two pairs of electrodes lengthways
the coupling path are attached - in the ge in Fig.2.

In the example shown, four pairs of electrodes are attached. |

Basically, the control voltage is further reduced as a result reducible that more than four pairs of electrodes are attached along ^ the coupling path of this directional coupler -1

i will be. t

Accordingly, the invention takes advantage of the fact that the light; speed is influ- .in the optical fibers particularly strongly influenced \ by particularly rapid change, ie particularly ί

I short lengths of the electric fields, generated by means of loading! ' especially many electrodes per light guide - despite a reduction in control voltages, even if the length of the coupling path is not changed. It is true that by extending the coupling section, you can also increase the heights
reduce the control voltages. Through the invention is
but it is possible without extending the coupling distance
simply by increasing the number of electrodes lengthways
this coupling path, so by reducing the size of the electrodes to reduce the control voltage. With the in Fig.

1 and 2, the coupling path has a length of 3 mm, for example, the electrodes in FIG

approx. 1.5 mm, in Fig. 2 approx. 0.7 mm in length. Because
the low control voltages can be used in the invention
often even a shortening of the length of the coupling path,
that is, a reduction in the space required on the substrate can be permitted.

2 protection claims. · \ 2 figures

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Directional coupler serving as a switch for optical signals in integrated technology, two light guides (AA ¹ , BB ¹ ) arranged in parallel along a coupling path on a substrate, 2.B. made of LiNbOj by means of Ti-doping, and wherein electrically controllable electrically conductive electrodes (E11 .... E24) are attached to the light guides along the coupling path, which, depending on the electrical control voltage (V1 - V2) between the electrodes , forward the light guided in the relevant light guide (AA ¹ ) directly (from A to A ¹ ) or pass it on exchanged crosswise between the light guides (from A to B ¹ ).

The level of the control voltage can be reduced by attaching at least two electrodes (E11 ... "E14, E21 ... ... E24) to each of the two light guides, one behind the other, so that one electrode (E11) on the first light guide (AA ¹ ) opposite an electrode (E21) on the second light guide (BB ¹ ), and that both opposing electrodes (E11 / E21, E12 / E22, ....), which each form a pair of electrodes, are separated from a different potential (V1 to E11, V2 to E21) of the control voltage (V1 / V2) can be controlled. Furthermore, each electrode (E11) on the first light guide (AA ¹ ) is electrically conductively connected to an electrode (E22) on the second light guide (B-B ') belonging to another, preferably adjacent pair of electrodes (E12 / E22).

(Fig. 2)

Claims (2)

• - • 20 1. Directional coupler serving as a switch for optical signals in integrated technology, where ^ two light guides (AA ¹ , BB ¹ ) arranged in parallel along a coupling path on a substrate j . e.g. made of LiNbO ^ by means of Ti doping, are attached, - to the. Light guides along the coupling path, respectively electrically controllable electrically conductive electrodes (E11 ... E24) are attached, which, depending on the electrical control voltage (V1-V2) between the . Electrodes in the relevant light guide (A-A ') Forward guided light directly (from A to A ') or interchangeably exchanged between the light guides forward (from A to B '), in particular for a switching network with purely optical intermediate lines in a telephone switching system, characterized in that _ at least two electrodes (E11 ... E14, E21 ... E24) are attached so that one electrode (E11) each on the first light guide (AA ¹ ) is opposite an electrode (E21) on the second light guide, both opposite electrodes (E11 / E21, E12 / E22 ,. .), each of which forms a pair of electrodes, each connected separately to a different terminal (V1 to E11, but V2 to E21) of the control voltage (V1 / V2) via a line, and - each electrode (E11) to the first light guide (AA ¹ ) is connected by means of a line to "one" of another, preferably adjacent electrode pair (E12 / E22) belonging to the electrode (E22) on the second light guide (BB ¹ ). - 7 - WP 62 85 DE 2. Directional coupler according to protection _{claim -j f} characterized in that - More than two pairs of electrodes are attached along the coupling path.