AU711623B2

AU711623B2 - An optical switch

Info

Publication number: AU711623B2
Application number: AU60545/96A
Authority: AU
Inventors: Johann Dr. Springer
Original assignee: Alcatel NV
Current assignee: Alcatel Lucent NV
Priority date: 1995-07-27
Filing date: 1996-07-17
Publication date: 1999-10-21
Anticipated expiration: 2016-07-17
Also published as: DE19527566A1; AU6054596A

Description

P/00/011 28/5/91 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "AN OPTICAL SWITCH" The following statement is a full description of this invention, including the best method of performing it known to us:- This invention relates to an optical switch in which an optical waveguide output can be switched at will to one of two optical waveguide inputs, which consists of a substrate on which a matrix of optical waveguides is provided and at the intersections of the optical waveguides diagonal channels are provided which are coupled to a device from which the channel can be filled with a liquid.

Such an arrangement is known (Article: "Low-Loss Intersecting Grooved Waveguides with Low D Delta for a Self-Holding Optical Matrix Switch in IEEE Transactions on Components, Packaging and Manufacturing Technology Part B, Vol.

18 No. 2, May 1 995, pages 241 to 244).

With the known optical switch, pot-like recesses are provided at one end of the diagonal channels. These recesses can be filled and emptied by a reservoir provided with a nozzle and moveable in all four directions When one of these recesses, and therefore also the corresponding diagonal channel, is filled with a liquid whose refractive index corresponds to that of the optical waveguide, then a linear, S uninterrupted transfer of the optical wave takes place at the intersection. If, on the other hand, the liquid is removed from the recess and therefore also from the diagonal channel at the intersection, then a boundary surface exists there with a large refractive index step to the refractive index of the air. By this means, due to total reflection, the optical wave is guided through such an angle, with low losses, that it is coupled into an optical waveguide diverging at right angles. Such an arrangement allows a switching of the optical wave at the intersection, from one optical waveguide to another. The known arrangement is very costly because of the required control for the filling and emptying of the reservoir, and for its positioning at a desired intersection of the optical waveguides.

According to the invention, there is provided an optical switch of the aforementioned kind, wherein: a) Each end of a channel is connected with a reservoir.

b) One reservoir contains a medium which has the refractive index of the optical waveguide core.

c) The other reservoir contains a medium with a refractive index which differs fromr the refractive index of the optical waveguide core.

d) Each reservoir contains a device which is capable of exerting pressure on the medium contained in it.

With such an optical switch, the switching of optical waves between two optical waveguides can be carried out with simple electrical means without masses having to be moved or liquids having to be filled or drawn out.

In order that the invention may be readily carried into effect, embodiments .15

S

thereof will now be described in relation to the accompanying drawings, in which: Figure 1 a shows a schematic representation for a design example of the optical switch of the invention, in one switch position, Figure 1 b shows the optical switch of Figure 1 a in the other switch position, Figure 2 shows a longitudinal section through an optical switch according to Figure 1 b, Figure 3 shows a longitudinal section through another design example of the optical switch, Figure 4 shows a longitudinal section through a further design example of the optical switch and Figure 5 shows the longitudinal section through yet another design example of the optical switch.

I

m Figure 1 a shows the top view of an intersection of the two optical waveguides 1 S and 2. There is a diagonally positioned channel 3 at the intersection and its two ends are respectively connected to a reservoir 4 or 5. The reservoirs 4,5 are almost filled with a liquid. Those parts 6 and 7 of the reservoirs 4 and 5 which are not filled with S liquid are full of air. In addition, the reservoirs 4 and 5 are provided with a device which is capable of exerting pressure on the liquids in the reservoirs. The devices shown in Figs. 1 a and 1 b for raising the pressure are heating devices 8 and 9. When such a heating device 8 or 9 is switched on, the volume of the medium in the spaces 6 or 7 is increased. For example, Figure 1 a shows one such state. The heating device 9 has been switched on. This has caused the volume of the medium in space 7 to increase, which has pushed the liquid from reservoir 5 into the channel 3. Since the liquid in reservoir 5 has a refractive index which is identical with that of the optical waveguide, the optical waves in the optical waveguide 1 continue straight ahead. This represents one switch position of the optical switch.

Figure 1 b clarifies the other switch position of the optical switch. In this switching state the volume of the medium in the space 6 has increased after the heating device 8 was switched on, which caused the liquid from the reservoir 4 to be pushed into the channel 3. Since the liquid in the reservoir 4 has a refractive index which is smaller than the refractive index of the optical waveguide, the optical waves from the optical waveguide 1 are directed into the optical waveguide 2. This is the other switch position of the optical switch.

Figure 2 clarifies the construction of an optical switch in accordance with Figs.

1 a and 1 b. It consists of a substrate 10, for example of silicon, in which corresponding grooves have been produced, for example by reactive ion etching. The substrate 10 is covered by a cover 11 which is joined to the substrate 10, for example by anodic bonding. In this way the reservoirs 4 and 5 are formed, as well as the 15 channel 3. The heating devices 8 and 9 can consist of thin-film resistors of TaN, NiCr o or another material, which are provided with low- resistance terminals.

Figure 3 shows a construction for the optical switch which differs from that shown in the design example of Figure 2. This design example also contains a substrate 10 and a cover 11. The reservoirs 4 and 5 are located in the substrate Through the opening 12, the reservoir 4 is continued into a sub-reservoir 13 whose upper surface is closed by the diaphragm 14. A piezoelectric element 15 is arranged on the diaphragm 14 in such a way that it can cause a contraction or expansion of the diaphragm. By operating the piezoelectric element 15, the volume of the subreservoir 13, and thus also of the reservoir 4, can be decreased which causes the liquid to be pushed from the reservoir 4 into the channel 3. In the cover 11 there is a ventilation hole 16 in the vicinity of the reservoir 5 which prevents the build-up of pressure in the reservoir 5. With the design example shown in Figure 3 the reservoir is filled with air.

The design example of the optical switch shown in Figure 4 differs from the construction in Figure 3 in that, above the reservoir 5 in the cover 11, there is also a sub-reservoir 18 which is connected to the reservoir 5 via the opening 17. With the design example shown in Figure 4, there is a liquid in the reservoir The design example shown in Figure 5 corresponds largely to the design example according to Figure 3. The difference between the two design examples consists of the optical switch in Figure 5 having no ventilation hole and having a diaphragm 14 with a magnetostrictive drive 20. In this design example, the pressure is exerted directly on the liquid by the diaphragm 14. The enclosed gas volume in the reservoir 5 produces a resetting back pressure.

With the design example shown in Figs. 1 a and 1 b, the heating devices are, for example, thin-film resistors. Instead of these, a radiation source can be used for producing heat, for example a laser beam directed at the gas volume. The membrane-like covers closing the reservoirs can also be made from a material with form memory, with a change in shape being produced by a heating device.

Claims

1. An optical switch in which an optical waveguide output an be switched on at will to one of two optical waveguide inputs, comprising a substrate on which a matrix of optical waveguides is provided and at the intersections of the optical waveguides a diagonal channel is provided which is coupled to a device from which the channel can be filled with a liquid, wherein: a) Each end of the channel is connected with a reservoir; b) One reservoir contains a medium which has the refractive index of the optical waveguide core; c) The other reservoir contains a medium with a refractive index which differs from the refractive index of the optical waveguide core; and d) Each reservoir contains a device which is capable of exerting pressure on the medium contained in it.

2. An optical switch as claim in Claim 1, wherein the media are liquids which are not S: miscible.

3. An optical switch as claimed in Claim 1, wherein one medium is a liquid and the other is a gas.

4. An optical switch as claim in any one of Claims 1 to 3, wherein at least one of the devices comprises a volume of gas contained in the reservoir, and a heating element is provided to heat said volume of gas.

An optical switch as claim in any one of Claims 1 to 3, wherein at least one of the devices comprises a diaphragm-like cover closing the reservoir and the cover is provided with a drive operated by a piezoelectric element.

6. An optical switch as claimed in any one of Claims 1 to 3, wherein at least one of the devices comprises a diaphragm-like cover closing the reservoir and the cover is provided with a drive operated by a magnetostriction.

7. An optical switch as claimed in any one of Claims 1 to 3, wherein both the reservoirs are provided with diaphragm-like covers which are provided with a drive operated by a piezoelectric element.

8. An optical switch as claimed in any one of Claims 1 to 3, wherein both the reservoirs are provided with diaphragm-like covers which are provided with a drive operated by magnetostriction.

9. An optical switch as claimed in Claim 4, wherein said heating element comprises a radiation source.

An optical switch as claimed in Claim 9, wherein the radiation source comprising a laser beam directed onto the volume of gas.

11. An optical switch as claimed in any one of Claims 1 to 3, wherein the device comprises a diaphragm-like cover closing the reservoir, said cover being made from a material with form memory and which is equipped with a heating element.

12. An optical switch as claimed in any preceding claim wherein the refractive index of the medium in said other reservoir is smaller than the refractive index of the optical waveguide core.

13. An optical switch substantially as herein described with reference to any embodiment shown in Figures 1 to 5 of the accompanying drawings. S. S S DATED THIS FOURTH DAY OF JULY 1996 S ALCATEL N.V. S S o. S. S S>