Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2000-10-06
2001-12-25
Lee, John D. (Department: 2874)
Optical waveguides
With optical coupler
Switch
Reexamination Certificate
active
06334009
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical signal switching apparatus using an optical switch that is used with optical communication equipment, etc. More specifically, the present invention relates to an optical signal switching apparatus that suppresses an incorrect action of the optical switch at the time of power on and/or power off.
Following speed-up and capacity increase of information transmission in recent years, an optical fiber network using an optical fiber and various optical devices has been introduced. The range of applications of the optical fiber network extends from the public communication networks to local area networks. An optical signal switching apparatus is one of the equipment used to realize an optical fiber network. An optical signal switching apparatus does not need to convert an optical signal into an electric signal which is switched to various routes, based on the converted electrical signal, in order to perform the switching function. Therefore, the construction of the optical fiber network becomes simple. Thus, the optical signal switching apparatus aids in realizing miniaturization and economization of the network.
There has been proposed for example, an optical cross connection equipment as an optical signal switching apparatus. An optical cross connection equipment is described in the “Photonics In Switching”, Technical Digest PTHA
5
1997 for example.
The optical signal switching apparatus generally includes an optical switch and an optical switch control unit. The optical switch is the key device of the optical signal switching apparatus. The use of a self holding type optical switch as the optical switch offers advantages due to its low consumption of electric power. The self holding type optical switch is an optical switch that maintain the state of the switch without the use of an electric power supply by using a permanent magnet, etc.
The structure of an optical signal switching apparatus is illustrated in FIG.
1
.
FIG. 1
illustrates that an optical switch control unit includes an optical switch driving unit and a power supply which supplies electric power to the optical switch driving unit. The optical switch driving unit generates a optical switch driving signal to drive the optical switch when an optical switch switching signal is detected. The optical switch driving unit transmits the optical drive signal to the optical switch. In
FIG. 1
, the optical inputs and optical outputs that are switched by the optical switch are omitted. A related optical signal switching apparatus is disclosed in Japan patent 2654437.
However the optical switch control unit described above does not take into consideration the noise that is originated in and generated by the turning on and/or off of power by the power supply. Therefore, it is easy for incorrect operation to occur at such times. More specifically, the noise originating in and generated by the tuning on and/or off of power by the power supply can possibly change the state of the optical switch that is being held.
The incorrect operation of the optical switch can result in the of loss not only large amounts of information but also has the possibility of inducing damage and a incorrect operation of other optical devices. For example, in a case where an optical switch is used with respect to a working system and a redundant system for protecting the working system, high reliability of the optical switch is required. It is essential that even when the electric power supply to the optical switch driving unit is interrupted, the optical switch should be maintained to the previously set state.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical signal switching apparatus that can maintain the state of an optical switch to a predetermined state at the time of turning on and/or off the power supply and at the time of output abnormality.
According to the present invention, the purpose of the above can be realized in an optical switch control unit with the following functions. The power state of the power supply of the optical switch control unit is supervised. When a predetermined condition of the output voltage of the power supply is satisfied, the optical switch driving unit is placed in an operation state. When the predetermined condition of the output voltage of the power supply is not satisfied, the optical switch driving unit is placed in a halt state. The operation state is a state where when an optical switch switching signal is input into the optical switch driving unit, an optical switch driving signal according to the optical switch switching signal is generated. The halt state is a state where even if an optical switch switching signal is input into the optical switch driving unit an optical switch driving signal is not generated.
The optical switch control unit includes an optical switch driving unit, a power supply which provides electrical power to the optical switch driving unit and a power supply surveillance unit which monitors the output voltage of the power supply and outputs a control signal to the optical switch driving unit. When the predetermined condition for the output voltage of the power supply is not satisfied, the control signal is generated. Detection of the control signal by the optical switch driving unit places the optical switch driving unit in the halt state.
According to the present invention, the purpose of the above is achieved by having an optical signal control unit and a self holding type optical switch.
REFERENCES:
patent: 4716357 (1987-12-01), Cooper
patent: 4909584 (1990-03-01), Imoto et al.
patent: 4946233 (1990-08-01), Seto
patent: 5905829 (1999-05-01), Maenishi et al.
patent: 6229932 (2001-05-01), Fukashiro et al.
patent: 915543 (1997-01-01), None
patent: 2654437 (1997-05-01), None
H. Sano, et al, “Photonics in Switching” Technical Digest PTHA5, 1997, pp. 83-87.
Fukashiro Yasuyuki
Hayashi Yukio
Kuwano Shinichi
Tsushima Hideaki
Yamahara Kenji
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Lee John D.
Song Sarah N
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