JPH04235533A - Light wavelength filtering device - Google Patents

Abstract

PURPOSE:To allow selective transmission of a unit input signal in a specific relation to a unit control signal by changing unit control signals of different wavelengths included in light control signals. CONSTITUTION:A light wavelength filtering device has means 1 to 4 whereby light control signals including more than one unit light control signals of different wavelengths are branched at each unit light control signal and means 5 to 8 whereby input light signals including a plurality of unit input light signals of different wavelengths are branched at each unit input light signal by means of individual light wavelength filter elements which allow wavelengths around different reference values to pass therethrough. The device also has means 9 to 12 to which each unit input light signal is input and which control transmission or nontransmission of each unit input light signal by means of a specific unit light control signal, and a means for synthesizing a plurality of transmitted unit input light signals together.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength filter device necessary for accurately performing large-capacity signal processing utilizing the broadband properties of optical signals in optical communication and optical signal processing.

0002

2. Description of the Related Art In recent years, optical communication has been put into practical use, and wavelength division multiplexing communication, optical communication line switching, coherent communication, etc. are being attempted with the aim of increasing the capacity of optical communication. Accordingly, there is a demand for optical functional elements such as wavelength tunable laser devices, tunable optical wavelength filter devices, and wavelength conversion laser devices. In particular, a tunable optical wavelength filter device is essential for selecting wavelength-multiplexed optical signals in wavelength division multiplexing communications. Conventionally, commonly used wavelength filter devices transmit or amplify input optical signals having wavelengths included in a transmission band centered on a certain wavelength.

0003

[Problem to be Solved by the Invention] In wavelength multiplexed optical communications, etc., in which signals are assigned to a plurality of different wavelengths, it is necessary to select and extract constituent optical signals from the wavelength multiplexed optical signal. . FIG. 5 is an explanatory diagram of an example of a wavelength filter device desired in technical fields such as wavelength division multiplexing optical communications.

In this figure, a control optical signal including a unit control optical signal of a plurality of different wavelengths, eg λa, λc, is used to generate a plurality of different wavelengths, eg λ1, λ2, λc.
Transmission or non-transmission of each wavelength of the input optical signal consisting of unit input optical signals of λ3 and λ4 is controlled, and a wavelength having a specific relationship with the unit control signal, for example λ1, is controlled from the input optical signal.
, λ3 are selected and output as transmitted optical signals.

If this function can be achieved, it will be possible to select a unit input optical signal that has a specific relationship with a unit control optical signal depending on the presence or absence of a unit control signal included in one control optical signal, which will facilitate the switching of optical communication lines. , signal selection becomes easier in optical signal processing and the like. Furthermore, this can be generalized to select a unit control optical signal included in a control optical signal and a unit input optical signal that corresponds to one-to-many, many-to-one, or many-to-many. This increases the degree of freedom in optical signal processing. In the above explanation, it is assumed that the transmission of the unit input optical signal is directly controlled by the unit control optical signal, but it is assumed that the unit control optical signal directly controls the transmission of the unit input optical signal. It is also possible to indirectly control the unit input optical signal by, for example, an electrical signal having .

However, a variable optical wavelength filter device that achieves the above function has not conventionally existed. Therefore, the present invention provides a variable control system that can selectively transmit unit input optical signals having a specific relationship with these unit control optical signals by changing unit control signals of different wavelengths included in the control optical signals. An object of the present invention is to provide an optical wavelength filter device.

[0007]

[Means for Solving the Problems] In the optical wavelength filter device according to the present invention, a control optical signal including unit control optical signals of one or more different wavelengths is transmitted for each unit control optical signal by a fixed optical wavelength filter element. An input optical signal containing a plurality of unit input optical signals of different wavelengths is demultiplexed into each unit input optical signal by an individual optical wavelength filter element that transmits wavelengths centered around different reference wavelengths. means for inputting each demultiplexed unit input optical signal, means for controlling transmission or non-transmission of the unit input optical signal by a specific unit control optical signal, and means for combining the plurality of transmitted unit input optical signals. In this invention, an input optical signal including a plurality of unit input optical signals of different wavelengths is wavelength-selected and transmitted using a control optical signal including one or more unit control optical signals of different wavelengths.

[0008] Furthermore, an input optical signal including one or more unit input optical signals having different wavelengths whose wavelengths are matched to a reference wavelength forming the center of the transmission band with an error within the transmission band width of the individual optical wavelength filter element; means for alternately switching a unit control optical signal whose wavelength matches one of the reference wavelengths and inputting it to the individual optical wavelength filter element; and means for transmitting the optical signal transmitted through the individual optical wavelength filter element to the output side and the individual optical wavelength filter element. The unit control optical signal is input to the individual optical wavelength filter element, both switching means are set so that it is transmitted to the individual optical wavelength filter element controller side, and the unit control optical signal transmitted through the individual optical wavelength filter element is received and converted by the electric signal. The operating conditions of the individual optical wavelength filter elements are controlled so that the individual optical wavelength filter elements obtain optimal transmission wavelength characteristics for the wavelength, and while the operating conditions of the individual optical wavelength filter elements are maintained as they are, Both switching means are set so that the input optical signal is input to the individual optical wavelength filter element and transmitted to the output side, and the wavelength selection operation of the input optical signal is performed.

[0009]

[Operation] Demultiplexes a control optical signal including unit control optical signals of different wavelengths into each unit control optical signal, and demultiplexes an input optical signal including unit input optical signals of multiple different wavelengths into unit input optical signals. Then, each unit input optical signal with a different wavelength is selectively transmitted by a unit control optical signal through a transmission controller, and the transmitted unit input optical signals are combined. By changing the unit control optical signal, the input It is possible to realize an optical wavelength filter device that selects and transmits a unit input optical signal of an arbitrary wavelength from optical signals. In addition, the input optical signal and a unit control optical signal whose wavelength matches one of the reference wavelengths are alternately input to the individual optical wavelength filter element, and the operating conditions of the individual optical wavelength filter element are determined using the unit control optical signal. Adjustments are made to obtain the optimum transmission characteristics, and by switching the input signal to the input optical signal while maintaining the operating conditions of the individual optical wavelength filter elements, changes over time of the individual filter elements are corrected, and the unit control light is In other words, it is possible to select the wavelength according to the unit control light while maintaining transmission characteristics that accurately match any of the reference wavelengths.

0010

[Examples] Examples of the present invention will be described below. (First Embodiment) FIG. 1 is a block diagram of a first embodiment of an optical wavelength filter device of the present invention. In this figure, FC is an optical wavelength filter for control optical signals, 1 to 4 are individual optical wavelength filter elements for control optical signals, FS are wavelength filters for input optical signals, 5 to 8 are individual wavelength filter elements for input optical signals, S
1 to S4 are light transmission controllers, ΛC is a control light signal, ΛS
is the input optical signal and ΛT is the transmitted optical signal.

In this embodiment, the control optical signal ΛC including unit control optical signals of wavelengths λa, λb, λc, and λd sent through the optical transmission line has wavelengths λa, λb, λc, and λd, respectively. The control light signal is demultiplexed into unit control light signals by a control light signal light wavelength filter FC having individual light wavelength filter elements 1, 2, 3, and 4 having a wavelength transmission band of . On the other hand, the data sent via other optical transmission lines,
An input optical signal Λ containing unitary input optical signals of multiple different wavelengths
S are different reference wavelengths λ1, λ2, λ3, respectively.
.

[0012] Each demultiplexed unit input optical signal is
Light transmission controllers S1, S2, S3, S4, respectively
The unit input optical signals that are input to each unit, transmitted or non-transmitted are controlled by unit control optical signals having a specific relationship, and transmitted through the optical transmitting light controller are combined again to form a transmitted optical signal ΛT
It is designed to be sent out as a single optical transmission line. In the above configuration, by simply changing the unit control optical signal included in the control optical signal, any unit input optical signal can be easily selected and transmitted from input optical signals including unit input optical signals of multiple different wavelengths. can be done.

[0013] By generalizing the above control and selecting unit input optical signals corresponding to the unit control optical signal included in the control optical signal in a one-to-many, many-to-one, or many-to-many manner, optical signal processing can be performed. The degree of freedom can be increased. In this case, as the fixed optical wavelength filter element, a dielectric multilayer filter, a waveguide filter, a spatial filter using a diffraction grating, etc. can be used, and as the light transmission controller,
For example, an optical/optical switch using a multiple quantum well structure can be employed.

(Second Embodiment) In the first embodiment, the wavelengths λa, λb, λc, λd of the unit control optical signals and the individual optical wavelength filters for input optical signals that separate the wavelengths of the unit input optical signals are used. Reference wavelength λ1 of the optical wavelength filter element,
Although no limitation was attached to the relationship between λ2, λ3, and λ4, it is possible to set the wavelength of the unit input optical signal and the wavelength of the unit control optical signal within an error within the passband width of the individual optical wavelength filter element for the input optical signal. Reference wavelengths λ1, λ2, λ3,
It is also conceivable to use one that matches one of λ4. In this way, the wavelength is λa = λ1, λb
= λ2, λc = λ3, λd = λ4, it is easy to keep the relative wavelength relationship between the unit control optical signal and the unit input optical signal constant, and optical communication or optical communication that operates stably can be achieved. An optical signal processing system can be constructed.

(Third Embodiment) FIG. 2 is a block diagram of a third embodiment of the optical wavelength filter device of the present invention, showing another configuration of the light transmission controller of the first embodiment. In this diagram,
21 is a light receiver, 22 is an electric circuit, and 23 is a laser amplifier. In this embodiment, selective transmission control of a unit input optical signal is performed electrically by a light transmission controller. The unit control light signal transmitted through the control light signal filter element is converted into an electric signal by a light receiver 21, and this electric signal is amplified by an electric circuit 22 as necessary to control a laser light amplifier 23. .

Therefore, when there is a unit control optical signal, the unit input optical signal input to the laser amplifier 23 is amplified and transmitted, and when there is no unit control optical signal, the unit input optical signal input is Absorbed and not transmitted. This circuit thus functions as a light transmission controller. In this embodiment, in addition to the laser amplifier, an electro-absorption optical modulator using the Franz Keldysh effect, a multi-quantum well structure optical modulator using the quantum-confined Stark effect, etc. can also be used.

(Fourth Embodiment) FIG. 3 is a block diagram of a fourth embodiment of the optical wavelength filter device of the present invention, which functions as a combination of an individual wavelength filter and a transmission controller. In this figure, 31 is a first optical path switch, 32 is an individual optical wavelength filter element, 33 is a second optical path switch, and 34 is an individual optical wavelength filter element controller. In this embodiment, an input optical signal is input to the input end A of the first optical path switch 31, and a unit control optical signal consisting of this and either one of the reference wavelengths is input to the other input end B. By switching the first optical path switch 31, one of these optical signals is input to the individual optical wavelength filter element 32, and the optical signal transmitted through this individual optical wavelength filter element 32 is switched to the second optical path switch. an output end C connected to the output waveguide by a device 33;
Then, it can be switched to an output end D connected to an individual optical wavelength filter element controller 34 that converts the optical signal into an electrical signal and electrically controls transmission/non-transmission of the individual optical wavelength filter element. The electric signal from the individual filter element controller 34 is transmitted to the transmission control terminal E of the individual optical wavelength filter element.
It is connected to the.

The operation of this embodiment will be explained. First, the first optical path switch 31 is switched to the B side, the second optical path switch 33 is switched to the D side, the unit control optical signal is passed through the individual optical wavelength filter element 32, and the unit control optical signal is passed through the individual optical wavelength filter element controller. Further, the electrical signal obtained by converting this optical signal is subjected to signal processing and guided to the transmission control end E of the individual optical wavelength filter element 32. In this state, the operating conditions of the individual optical wavelength filter elements 32 are adjusted by the individual optical wavelength filter element controller 34 so that the maximum number of unit control optical signals are transmitted. Note that this adjustment can be automatically performed by an electric circuit.

Next, while maintaining the above operating conditions,
By switching the first optical path switch 31 and the second optical path switch 33, the input optical signal is input to the individual optical wavelength filter element, and the element functions as the original individual filter element. As mentioned above, the unit control optical signal is one of the reference wavelengths, and the unit input optical signal that matches this reference wavelength within the transmission bandwidth of the input optical signal is automatically set to the optimum transmission band of the individual filter element. It will come in. That is, only the unit input optical signal near the unit control light is transmitted. Therefore, even if the individual optical wavelength filter elements inherently have characteristics that change over time, accurate transmission characteristics can be maintained by repeating the above control of the transmission band at appropriate time intervals. Note that if there is no unit control optical signal, in the case of an active filter, if the bias is lowered, the filter becomes non-transmissive, so it is sufficient to control it in this manner.

FIGS. 4A and 4B are explanatory diagrams of individual optical wavelength filter elements that can be used in the fourth embodiment of the present invention. In this figure, 41 is a waveguide and 42 is a diffraction grating. FIG. 4(A) shows an example of the configuration of an optical wavelength filter element. This device has a distributed feedback laser (DFB) structure having a diffraction grating 42 along a waveguide 41 consisting of a semiconductor active layer and a waveguide layer, and inputs an input optical signal parallel to the waveguide. A transmission amplified optical signal is output from the other end. The active layer forming the waveguide is biased slightly below the threshold at which the device oscillates as a DFB laser.

FIG. 4B shows the relationship between the bias voltage and the transmission wavelength band of the above optical wavelength filter element. As shown in this figure, the transmission wavelength band of this type of optical wavelength filter element is a very narrow band (~0.5 Å), and the wavelength selectivity is excellent. However, when using this in an optical communication system, etc., the transmission band changes depending on the bias voltage, so in order to match the transmission band to the wavelength of the input optical signal, it is necessary to precisely adjust the temperature and operating voltage of the element. Must be set. However, even if the operating current and temperature are controlled to be constant, the center wavelength of the transmission band may shift if the characteristics of the element itself change due to changes over time or the like. In that case, it becomes impossible to transmit an input signal of a desired wavelength with maximum transmittance, and further, crosstalk between input optical signals of adjacent wavelengths increases. According to this embodiment, by taking advantage of the fact that the transmission band changes depending on the bias voltage, as described above, the change in the transmission band over time is corrected by appropriately adjusting the transmission band using the unit control optical signal, Accurate transmission characteristics can be maintained.

[0022] Furthermore, in a distributed feedback laser type optical wavelength filter element, the operating current must be set slightly low near the oscillation threshold state so that the optical wavelength filter element does not oscillate itself as a DFB laser and emit light. However, the reference optical signal is intensity-modulated by turning it on and off in about 50 msec,
When there is no reference optical signal, it is possible to perform control to set the electrical operating conditions just below the oscillation threshold, and when there is a reference optical signal, it is possible to control the center wavelength of the transmission band. Therefore, the transmission band and the oscillation threshold can be controlled quickly and easily.

In this embodiment, the specific configuration used is a phase shift adjustable DF as a transmission controller.
A B semiconductor laser type filter element can be used. As the optical path switch, an InP-based directional coupler type optical switch or a carrier injection type total reflection optical switch is used, and by applying a voltage or flowing a current to its control terminal, a unit input optical signal can be changed into two. It is possible to switch between the two inputs A, B and the two outputs C, D in a crosswise or parallel manner. Furthermore, a PIN photoreceiver can be used as the element that converts the optical signal transmitted through the individual optical wavelength filter element into an electrical signal and uses it as a control signal. Furthermore, the optical signals are coupled through an optical waveguide such as an optical fiber, and after being converted into an electrical signal, are coupled via electrical wiring.

[0024]

[Effects of the Invention] As explained above, according to the present invention,
By simply changing the unit control optical signal included in the control optical signal, any single or multiple unit input signals included in the input optical signal can be selected and transmitted, making it easy to replace optical communication lines and optical signals. In processing systems, it becomes easier to select optical signals, and it becomes easier to perform processing such as switching and branching between signals in each wavelength band.
Signal processing capacity can be substantially expanded.

[0025] Furthermore, after adjusting the operating conditions so that the individual optical wavelength filter element controller provides an appropriate transmission band using a reference optical signal having approximately the same wavelength as the unit input optical signal,
In order to input the input optical signal to the individual optical wavelength filter element,
Accurate transmission characteristics can be maintained by correcting changes over time that the individual optical wavelength filter elements inherently have. Therefore, the present invention greatly contributes to qualitative improvement in the field of wavelength multiplexed optical signal processing technology.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a first embodiment of an optical wavelength filter device of the present invention.

FIG. 2 is a configuration diagram of a third embodiment of the optical wavelength filter device of the present invention.

FIG. 3 is a configuration diagram of a fourth embodiment of the optical wavelength filter device of the present invention.

FIG. 4 is an explanatory diagram of an individual optical wavelength filter element that can be used in the fourth embodiment of the present invention, in which (A) shows the configuration of the variable wavelength optical filter element, and (B) shows the relationship between the bias voltage and the transmission wavelength band. It shows.

FIG. 5 is an explanatory diagram of an example of an optical wavelength filter device desired in technical fields such as wavelength division multiplexing optical communications.

[Explanation of symbols]

1-4 Individual wavelength filter elements for control optical signals 5-8
Individual wavelength filter element FC for input optical signal Optical wavelength filter FS for control optical signal Optical wavelength filter S1 to S4 for input optical signal Optical transmission controller ΛC Control optical signal ΛS Input optical signal ΛT Transmitted optical signal

Claims (4)

[Claims] 1. Means for demultiplexing a control optical signal including one or more unit control optical signals of different wavelengths into each unit control optical signal by a fixed optical wavelength filter element, and a plurality of unit input optical signals of different wavelengths. means for demultiplexing input optical signals containing each unit input optical signal by individual optical wavelength filter elements that transmit wavelengths centered around different reference wavelengths; , a means for controlling transmission or non-transmission of a unit input optical signal by a specific unit control optical signal, and a means for multiplexing a plurality of transmitted unit input optical signals. What is claimed is: 1. An optical wavelength filter device that selects the wavelength of an input optical signal including a control optical signal including a unit control optical signal having one or more different wavelengths, and transmits the input optical signal. [Claim 2] The wavelength of each of the unit input optical signals having a plurality of different wavelengths is made to match one of the reference wavelengths with an error within the transmission bandwidth of the individual optical filter element. The optical wavelength filter device according to claim 1. 3. An input optical signal including one or more unit input optical signals having different wavelengths whose wavelengths are matched to a reference wavelength forming the center of the transmission band with an error within the transmission band width of the individual optical wavelength filter element; Means for alternately switching a unit control optical signal whose wavelength matches one of the reference wavelengths and inputting it to the individual optical wavelength filter element, and a means for inputting the optical signal transmitted through the individual optical wavelength filter element to the output side and the individual optical wavelength filter. It consists of a means for alternately switching to the element controller side, and a means for inputting an electrical signal obtained by converting the transmitted unit control optical signal to the individual optical wavelength filter element via the individual optical wavelength filter element controller. Both switching means are set so that the signal is input to the individual optical wavelength filter element and transmitted to the individual optical wavelength filter element controller side, and the unit control optical signal transmitted through the individual optical wavelength filter element is received and converted by the electrical signal. The operating conditions of the individual optical wavelength filter elements are controlled so that the individual optical wavelength filter elements obtain optimal transmission wavelength characteristics for the wavelength, and while the operating conditions of the individual optical wavelength filter elements are maintained as they are, An optical wavelength filter device characterized in that an input optical signal is input to an individual optical wavelength filter element and both switching means are set so that the input optical signal is transmitted to the output side to perform a wavelength selection operation of the input optical signal. 4. The optical wavelength filter device according to claim 3, wherein light whose intensity is modulated on and off is used as the reference optical signal.