Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-11-01
2003-04-15
Chan, Jason (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S108000
Reexamination Certificate
active
06549314
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical control apparatus, an optical junction apparatus and an optical ADM apparatus and an optical transmission apparatus having the apparatus.
2. Description of Related Art
High reliability is requested in an optical submarine system. In such a system, a detour path is prepared as an auxiliary optical transmission system route in preparation for a case in which trouble is caused in a certain repeater or a cable. There is needed an optical junction apparatus for switching to transmission by the detour path when trouble is caused.
In the meantime, according to the optical junction apparatus in the above-described system, path switching must frequently be operated remotely when trouble is caused after a trouble spot has been specified by a test signal from an end office apparatus or the like. Therefore, the optical junction apparatus is requested to be able to operate to switch by a control signal from a remote location. As an optical junction apparatus capable of carrying out such a switching operation, there has conventionally known a constitution incorporating an optical switch for switching an optical path by mechanically moving an optical part such as a prism or the like by receiving a control signal from outside.
On the other hand, in order to deal with large capacity formation of a transmission capacity in recent years and to construct a flexible network among a plurality of stations, there has been reduced to practice wavelength division multiplexing optical transmission (hereinafter, referred to as “WDM optical transmission”) using optical ADM apparatus. According to the WDM optical transmission using optical ADM (add-drop multiplexer) apparatus, optical ADM apparatus are arranged at transit stations arranged among end offices. End offices and transit stations are connected by optical transmission paths and there is transmitted wavelength division multiplexing light (hereinafter, referred to as “WDM signal light”) in which a plurality of signal light having wavelengths different from each other are subjected to wavelength division multiplexing. Signal light having respective wavelength is allocated to respective channel.
The optical ADM apparatus is provided with a function of separating signal light from WDM signal light inputted from an optical transmission path as necessary and inserts the signal light into the optical transmission path when the optical ADM apparatus transmits from a certain transit station to the optical transmission path. There is known a conventional constitution in which in order to separate signal light inputted from an optical transmission path, for example, WDM signal light is temporarily divided into respective wavelengths of signal light by an optical wavelength division demultiplexer. According to the constitution, there is arranged an optical switch for respective divided signal light and by switching the optical switch, there is carried out a selection whether the respective signal light is to be separated to a side of a transit station or transmitted to the optical transmission path as it is.
However, according to the above-described conventional optical division apparatus or optical ADM apparatus, in any of the constitutions, in order to carry out optical path switching or selective sampling of signal light, an optical switch having a movable portion is used and accordingly, there is a certain limit in view of the reliability. Further, according to the optical ADM apparatus, it is also difficult to control separation and insertion of the optical ADM apparatus by a control signal from an end office or the like disposed upstream from the transit station. Levels of signal light which passes through the optical ADM apparatus and is shortcircuited and signal light newly inserted into the optical ADM apparatus need to be the same. However, there also is a case in which depending on the constitution of the optical ADM apparatus, the levels of both significantly differ from each other and the level of the signal light outputted from an optical amplifier needs to adjust.
SUMMARY OF THE INVENTION
It is a first object of an optical control apparatus, an optical junction apparatus and an optical ADM apparatus and a WDM optical transmission apparatus using thereof according to the present invention is being capable of controlling optical path switching operation and selective separation and insertion of signal light from outside with high reliability. A second object thereof resides in that adjustment of an output level of signal light outputted from an optical amplifier arranged in an optical ADM apparatus is made unnecessary.
According to an aspect of the present invention, there is provided an optical control apparatus comprising an optical reflector for selectively reflecting only signal light having a specific wavelength in inputted signal light and transmitting signal light having other wavelength and outputting transmitted signal light and a saturable absorber inputted with the transmitted signal light for transmitting the transmitted signal light and outputting first output signal light only when an output level of the transmitted signal light is equal to or larger than a predetermined threshold value. In this case, the optical reflector is inputted further with control signal light in addition to the signal light and when a wavelength of the control signal coincides with the specific wavelength, an output level of the signal light is set to be lower than the threshold value. Conversely, when the wavelength of the control signal does not coincide with the specific wavelength, a sum of the output level of the signal light and an output level of the control signal light is set to exceed the threshold value. The optical reflector can be constituted by using fiber gratings.
The optical junction apparatus according to the present invention is further provided with two optical couplers with the above-described optical control apparatus of the present invention as the basic constitution and carries out division and insertion of signal light by these optical couplers. Specifically, the optical junction apparatus according to the present invention is provided with a first optical coupler for dividing inputted signal light and outputting first divided signal light and second divided signal light, a first optical reflector, a first saturable absorber and a second optical coupler. The first optical reflector is inputted with first divided signal light, reflects selectively only light having a first specific wavelength, transmits light having other wavelength and outputs transmitted signal light. The first saturable absorber is inputted with the transmitted signal light, transmits the transmitted signal light only when an output level of the transmitted signal light is equal to or larger than a predetermined first threshold value and outputs first output signal light. The second optical coupler outputs the first inputted output signal light or second output signal light in the first output signal light and the second output signal light.
According to the above-described constitution, the first optical coupler is further inputted with control signal light in addition to the signal light. When a wavelength of the control signal light coincides with the first specific wavelength, the output level of the signal light inputted to the first saturable absorber is set to be lower than the first threshold value and when the wavelength of the signal light does not coincide with the first specific wavelength, a sum of the output level of the signal light and an output level of the control signal light which are inputted to the first saturable absorber are set to exceed the first threshold value. By adding the control signal light to the signal light, the output of the original signal light can be controlled by controlling the wavelength of the control signal light. Addition of the control signal light to the signal light can be carried out by using light having wavelengths
Chan Jason
Dickstein , Shapiro, Morin & Oshinsky, LLP
Li Shi K.
NEC Corporation
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