Optical switcher used for broadcast station

To provide an optical switcher capable of sending incident light on one input port to any plurality of output ports. The optical switcher includes input ports disposed on extensions of m input optical paths (m being 2 or greater natural number), output ports disposed on extensions of n output optical paths (n being 2 or greater natural number), and movable translucent switch mirrors 311-3mn, disposed at intersections of the m input optical paths and the n output optical paths, for switching between the input optical paths and the output optical paths. A switch mirror 311-3mn located nearer the input ports has a higher transmittance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical switcher used in a signal transmission/distribution system or the like used in a broadcast station.

2. Description of the Related Art

In the past, optical switchers having a plurality of inputs and outputs have been developed for cross connection in a trunk transmission network. In general, cross connection in the trunk transmission network is only required to implement a N-to-N nonblocking switching, and is not required to implement a one-to-N broadcasting mode connection. To the contrary, switchers used in a broadcast station or the like are required to have a capability of signal distribution, and thus, the one-to-N broadcasting mode connection is required. Conventionally, only switching of an uncompressed SDTV (Standard Definition Television) serial digital signal transferred at a rate of 270 Mb/s at most was needed, and thus, the one-to-N broadcasting mode connection could be readily realized electrically by electrical switchers.

Recently, broadcast stations have been required to transmit and switch an uncompressed HDTV (High Definition Television) serial digital signal at a transfer rate of 1.5 Gb/s. In order to transmit the serial digital signal at a rate of 1.5 Gb/s for 100 meters or more, optical fiber transmission is essentially used. At present, as shown inFIG. 1, optical fiber transmission and an electrical switcher are used. InFIG. 1, reference numeral101denotes an electric-optic (E/O) converter for converting an input serial digital signal into an optical signal, reference numeral102denotes an optical fiber for transmitting the optical signal sent from the E/O converter101, reference numeral103denotes an opto-electric (O/E) converter for converting the optical signal received from the optical fiber102into an electric signal (serial digital signal), reference numeral104denotes an electrical switcher for switching the serial digital signal, reference numeral105denotes an E/O converter for converting the serial digital signal output from the electrical switcher104into an optical signal, reference numeral106denotes an optical fiber for transmitting the optical signal sent from the E/O converter105, and reference numeral107denotes an O/E converter for converting the optical signal received from the optical fiber106into an electric signal (serial digital signal).

In such a conventional signal transmission/distribution system, the O/E converters103, the O/E converter105and the electrical switcher104are necessarily located on the optical fiber transmission path. Therefore, the system becomes disadvantageously complicated. If an optical switcher enabling one-to-N broadcasting mode connection is provided, transmission and switching can be accomplished optically, and thus, the system can be simplified and the cost can be reduced.

SUMMARY OF THE INVENTION

The present invention has been devised to solve such a problem. Accordingly, an object of the present invention is to provide an optical switcher capable of sending incident light on one input port to any plurality of output ports.

An optical switcher according to the present invention comprises: input ports (21-2m) disposed on extensions of m input optical paths (m being 2 or greater natural number); output ports (41-4n) disposed on extensions of n output optical paths (n being 2 or greater natural number); and movable switch mirrors (311-3mn), disposed at intersections of the m input optical paths and the n output optical paths, for switching between the input optical paths and the output optical paths, in which the movable mirrors are translucent mirrors.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring toFIG. 2showing a perspective view of an optical switcher of the first embodiment according to the invention andFIG. 3illustrating broadcasting mode connection in the optical switcher ofFIG. 2, the optical switcher has a plurality of outputs and enables the one-to-N broadcasting mode connection (N being a natural number). In the optical switcher inFIG. 2, for example, incident light on the i-th input is to be sent to any plurality of outputs, specifically, the j-th, k-th and l-th outputs.

As shown inFIG. 2, the optical switcher according to the invention comprises m input optical fibers11-1m(m being 2 or greater natural number), input collimator lenses21-2mdisposed at m input ports associated with the input optical fibers11-1m, respectively, m-by-n translucent switch mirrors311-3mn(n being 2 or greater natural number), m-by-n drive mechanisms each composed of a power source, such as a piezoelectric actuator that is displaced depending on an external control signal, and transmission means for transmitting the displacement of the power source to the associated one of the translucent mirrors311-3mnto cause the same to rotate, output collimator lenses41-4ndisposed at n output ports, n output optical fibers51-5n, input collimator lenses21-2m, translucent switch mirrors311-3mn, and a base6on which the drive mechanisms and the output collimator lenses41-4m, are mounted.

Each of the translucent switch mirrors311-3mnis provided with its own drive mechanism. The drive mechanism enables each of the switch mirrors311to3mnto assume, independently of others, an upright position in which it reflects part of propagation light incident from the associated input collimator lens (input optical path) toward the associated output collimator lens or a laid position in which it does not intercept the propagation light from the associated input collimator lens to allow it to travel straight ahead. The positions of the translucent switch mirrors311-3mncan be controlled by applying control signals to their respective drive mechanisms from an external control circuit.

Of course, the switch mirrors311,312,313, . . . ,31nare associated with the input collimator lens11, the switch mirrors3(m−1)1,3(m−1)2,3(m−1)3, . . . ,3(m−1)nare associated with the input collimator lens1m−1, the switch mirrors3m1,3m2,3m3, . . . ,3mnare associated with the input collimator lens1m, the switch mirrors311,321,331, . . . ,3m1are associated with the output collimator lens41, the switch mirrors312,322,332, . . . ,3m2are associated with the output collimator lens42, and the switch mirrors31n,32n,33n, . . . ,3mnare associated with the output collimator lens4n.

Now, referring toFIG. 1, an operation of the optical switcher according to this embodiment will be described in detail. For example, an optical signal input via the input optical fiber1mis converted into parallel light by the input collimator lens2mto propagate in a space. If the switch mirror3m1is in the upright position, the propagation light is reflected by the switch mirror3m1toward the output collimator lens41, absorbed into the output collimator lens41, and then sent (coupled) to the output optical fiber51.

If the switch mirror3m1is in the laid position, the propagation light travels straight ahead without being reflected toward the output collimator lens41. In this way, the optical signal input via the input optical fiber1mcan be switched to the output optical fiber51by controlling the rotation angle of the switch mirror3m1.

Similarly, the optical signal input via the input optical fiber1mcan be switched to the output optical fibers52-5nby controlling the rotation angles of the switch mirrors3m2-3mn, respectively. The operation described so far is the same as that of conventional optical switchers and the switch mirrors311-3mnhave been assumed to be total reflection mirrors. However, according to this embodiment, the switch mirrors311-3mnare translucent mirrors (half mirrors). Consequently, according to this embodiment, the one-to-N broadcasting mode connection can be realized. Now, an example of the one-to-N broadcasting mode connection will be described with reference to FIG.1.

For example, an optical signal input via the input optical fiber1m−1is converted into parallel light by the input collimator lens2m−1to propagate in a space. If the switch mirror3(m−1)1is in the upright position, part of the propagation light is reflected by the switch mirror3(m−1)1toward the output collimator lens41and sent to the output optical fiber51through the output collimator lens41.

The remaining part of the propagation light, which has passed through the switch mirror3(m−1)1, travels straight ahead and, if the switch mirror3(m−1)2is in the upright position, is partially reflected by the switch mirror3(m−1)2toward the output collimator lens42and sent to the output optical fiber52through the output collimator lens42. The remaining part of the propagation light, which has passed through the switch mirror3(m−1)2, travels straight ahead and, if the switch mirror3(m−1)nis in the upright position, is reflected by the switch mirror3(m−1)ntoward the output collimator lens4nand sent to the output optical fiber5nthrough the output collimator lens4n.

Similarly, the optical signal input via the input optical fiber1m−1can be switched to the output optical fibers51-5nby controlling the angles of the switch mirrors3(m−1)1-3(m−1)non the optical path, respectively, in any one-to-N broadcasting mode. Furthermore, according to this embodiment, a translucent switch mirror located nearer the input collimator lenses21-2mhas a higher transmittance. In other words, a translucent switch mirror located nearer the input collimator lenses21-2mhas a lower reflectance. This transmittance/reflectance arrangement generally can reduce variations in the powers of the optical outputs in the one-to-N broadcasting mode switching.

In the first embodiment, the translucent switch mirrors311-3mnhave been described as rotary type switch mirrors capable of assuming two, upright and laid, positions, as shown in FIG.4(a). Alternatively, as shown in FIG.4(a), the translucent switch mirror may be a linear type switch mirror that is moved linearly between a position in which it reflects part of propagation light incident from the associated input collimator lens toward the associated output collimator lens and a position in which it allows the propagation light to travel straight ahead without interception. For driving the mirrors3, driving mechanism3asuch as piezoceramics is applied to each of the mirror3.

FIG. 5shows driving circuit arrangement. InFIG. 5, a controller7delivers driving signals for each of the driving mechanism3aarranged at each of cross points in the optical switch matrix module8. If piezoceramics is applied as the driving mechanism3a, the controller7supplies certain voltages to the piezoceramics though amplifiers.

Furthermore, the base6and the translucent switch mirrors311-3mncan be implemented as a microelectro-mechanical system (MEMS) by forming them in a silicon substrate by a semiconductor process. Hereinafter, a second embodiment according the present invention formed in a silicon substrate will be described with reference to theFIGS. 6,7, and8. InFIG. 6showing a plain view of the second embodiment, a translucent mirror plate3′, springs11and projecting supports13are made of the same substrate of polySilicon. As shown inFIGS. 7 and 8respectively showing sectional views in A-A′ and B-B′ axes ofFIG. 6, the mirror plate3′ and springs11are supported by the supports13and positioned above a substrate9of Silicon (Si). In the substrate9, trench14is formed and its surface is covered by SiN deposition. Further, metal material such as aluminum (Al) 12 is deposited on a part of the trench wall as shown in FIG.7and thus the mirror plate3′ can be rotated in the trench14by electrostatic attraction between the metal material12and the mirror plate3′ when a voltage is supplied to the metal material12. To supply the voltage, a metal wiring pattern12′ is also arranged on the substrate9. In the second embodiment, transmittance of the mirror plate3′ can be controlled by thickness of the mirror plate3′, for example.

FIGS.9(a)-9(d) and FIGS.10(a)-10(d) show producing processes of the optical switcher of the second embodiment. As shown in FIGS.9(a) and9(b), the trench14is produced in the Si-substrate9(first wafer) by RIE (Reactive Ion Assisted Etch) dry etching and a projecting portion is formed on the substrate9by the RIE dry etching. Further, as shown in FIG.9(c), the SiN is deposited on the substrate9and after this, as shown in FIG.9(d), the metal material12on the part of the trench wall and the wiring pattern12′ are arranged on the substrate9. Next, to produce the mirror plate3′, spring11and support13, another SOI (Silicon on Insulator) substrate (second wafer) shown in FIG.10(a) is prepared. As shown in FIG.10(b), the patterns corresponding to the mirror plate3′, spring11and support13are produced in the polysilicon layer of 10 m by silicon RIE etching. After this, as shown in FIG.10(c) the first wafer and second wafer are bonded by heat treating at 1200 C. Finally, the layers of Si(500 m) and SiO2(0.5 m) of FIG.10(c) are removed by the RIE etching.

Furthermore, according to the present invention, an optical fiber array may be used as the input optical fibers11-1mand the output optical fibers51-5n, and a microlens array may be used as the input collimator lenses21-2mand the output collimator lenses41-4n.

According to this invention, by using the translucent mirrors as the movable switch mirrors in the m by n matrix, the optical switcher capable of sending incident light on one input port to any plurality of output ports can be provided. Thus, the optical switcher enabling the one-to-N broadcasting mode connection can be provided, and the system can be simplified and the cost can be reduced compared with the conventional signal transmission/distribution system including the photoelectric converters and the electrical switcher.

Furthermore, since a movable switch mirror located nearer the input port has a higher transmittance, the variations in the powers of the optical outputs appearing when incident light on one input port is sent to any plurality of output ports can be reduced.