JPH095801A - Optical signal processing circuit - Google Patents

Abstract

PURPOSE: To eliminate the crosstalks by the reinput of an input waveguide and to make arbitrary nonequal channel arrangement possible by inputting the output of the output waveguide of a first period to the output waveguide of a second period and obtaining the output signal from the output waveguide of the second period. CONSTITUTION: The light signal inputted to an input port I4 is demultiplexed by an array waveguide grating 10 and is outputted to the output ports O1 to O8 of the first period corresponding to each of wavelengths. The light signal emitted from the output port Oi returned to the output port Oi+ N corresponding as it is if the corresponding i-th 2×2 optical switches 30 is a bar state and is outputted to a branching port in the case of a cross state. The light signal enters the output port Oi+ N of a grating 10 if the light signal is inputted from the insertion port at the time of the cross state. The light signals entering the output ports O9 to O16 are outputted again from the input port I12 multiplexed by the grating 10 as the input and output waveguide arrangements, i.e., port arrangements, are the same in the first period and the second period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to optical frequency division multiplexing (FD).
M) Used for communication. In particular, the present invention relates to an optical signal processing circuit in which an optical signal subjected to optical frequency division multiplexing is once separated, processed, and then multiplexed again. The present invention is particularly suitable for use in an optical add / drop circuit for inserting or removing an arbitrary optical signal.

Although the term "optical frequency division multiplexing" is used in this specification, the frequency and wavelength of light correspond to each other, and "optical frequency division multiplexing" means "wavelength division multiplexing (WD).
M) ”.

[0003]

2. Description of the Related Art 1.5 μ, which is a low loss region of an optical fiber
In m-band optical transmission, a dispersion shift fiber is used in order to reduce transmission waveform deterioration due to wavelength dispersion of the optical fiber. Also, in recent years, in order to expand the transmission capacity, many wavelengths /
A wavelength division multiplexing / optical frequency division multiplexing transmission method for multiplexing and transmitting optical signals of frequencies has been developed. However, when light of a plurality of wavelengths is simultaneously transmitted in the region near the zero-dispersion wavelength of the optical fiber, the four-wave mixing phase matching condition, which is one of the nonlinear effects of the optical fiber, is easily established. Therefore, in the optical frequency division multiplex transmission using the dispersion shift fiber, crosstalk occurs between the optical frequency channels and the transmission characteristics deteriorate. The crosstalk due to the four-wave mixing becomes the largest when the channels are arranged at equal intervals. Therefore, some channel arrangement methods have been proposed in which the channels are arranged at unequal intervals to reduce crosstalk due to four-wave mixing.

On the other hand, as an optical signal processing circuit for extracting and processing an arbitrary optical signal from an optical signal subjected to optical frequency division multiplexing, one using an arrayed waveguide grating has been proposed.
Conventional arrayed waveguide devices had only equal channel intervals, but recently it has been utilized that the imaging position on the output focal plane of the arrayed waveguide grating is proportional to the optical frequency. Then, by arranging the output waveguide positions at unequal intervals, array waveguide elements capable of multiplexing and demultiplexing optical signals at unequal channel intervals have been developed.

FIG. 2 shows a configuration example of an optical add / drop circuit that extracts or inserts an optical signal as a conventional optical signal processing circuit using an unequal channel spacing arrayed waveguide grating. Here, an example in which the number of channels N = 15 will be described. This optical add / drop multiplexer is provided with an arrayed waveguide grating 20, and the arrayed waveguide grating 20 has an unequal spacing arrangement corresponding to a channel arrangement in which the channel frequencies of the optical signals subjected to the optical frequency division multiplexing are unequal spacings. 16 input waveguides 2 with
1 and output waveguide 25 and two fan-shaped slab waveguides 2
2, 24 and the arrayed waveguide 25 in which the optical path length difference is increased at a predetermined interval are connected in the order of the input waveguide 21, the slab waveguide 22, the arrayed waveguide 23, the slab waveguide 24, and the output waveguide 25. The input waveguide 21 and the output waveguide 25 have a structure and form the input ports I _{1 to} I ₁₆ and the output ports O _{1 to} O ₁₆ , respectively. The optical frequency-multiplexed signal is input to the input port I _8, and the optical signal after the dropping and adding is output from the output port O ₈ . Other input port I ₁
To I ₇ , I _{9 to} I ₁₆ and output ports O _{1 to} O ₇ , O ₉
~ O ₁₆ is between the corresponding port is connected via a 2 × 2 optical switch 30. That is, the input port I _i
(I = 1 to 7, 9 to 16) and the output port O _i are connected via the i-th 2 × 2 optical switch 30 to form a loopback configuration.

In the i-th 2 × 2 optical switch 30, one input SW-in1 is connected to the output port O _i of the arrayed-waveguide grating 20, and the other input SW-in2 is input with an insertion optical signal. It is connected to an insertion port (not shown). Further, one output SW-out1 is connected to the input port I _i of the arrayed waveguide element 20, and the other output S-out1.
W-out2 is connected to a branch port (not shown) that outputs a branch optical signal. The connection states that the 2 × 2 optical switch 30 can take are the input SW-in1 and the output SW-o.
ut1, a bar state in which the input SW-in2 and the output SW-out2 are connected, and the input SW-in1 and the output SW-ou
There are two types, t2, and a cross state in which the input SW-in2 and the output SW-out1 are connected.

The optical signal input to the input port I ₈ is demultiplexed by the arrayed waveguide grating 20 and output to the output ports O _{1 to} O ₇ and O _{9 to} O ₁₆ corresponding to the respective wavelengths.
The optical signal output from the output port O _i has the corresponding i-th 2
If the × 2 optical switch 30 is in the bar state, it is directly returned to the corresponding input port I _i , and if it is in the cross state, it is output to the branch port. In the cross state, if an optical signal is input from the insertion port, the optical signal enters the input port I _i of the optical waveguide grating 20. Input port I
_The optical signals entering _{1 to} I ₇ and I _{9 to} I ₁₆ are combined again by the arrayed waveguide grating 20 and output from the output port O ₈ .

In general, the arrayed waveguide grating has symmetry in the coupling wavelength between the ports, and the wavelength coupling from the jth input port to the kth output port is from the kth input port to the jth output port. Join. Therefore, when the light output from the input port I _j to the output port O _k is input to the input port I _k , the light is always output to the output port O _j even if the arrayed waveguide grating 20 has an unequal channel arrangement.
Output from Therefore, the loopback configuration described above can be used as an optical add / drop circuit.

[0009]

However, in the above-mentioned conventional example, since the optical signal once demultiplexed by the arrayed-waveguide grating is input to the input port of the arrayed-waveguide grating again, crosstalk light is not generated. It becomes a problem.

The present invention solves such a problem, and an optical signal capable of demultiplexing, processing, and multiplexing an optical frequency division multiplexed signal arranged at unequal channel intervals with almost no generation of crosstalk light. An object is to provide a processing circuit.

[0011]

The optical signal processing circuit of the present invention comprises means for demultiplexing an input optical signal in which channel frequencies are multiplexed at unequal intervals by wavelength, and individual demultiplexed optical signals. A plurality of processing means for performing processing, and means for recombining the optical signals respectively processed by the plurality of processing means, wherein the demultiplexing means and the combining means are provided between two fan-shaped slab waveguides. Is composed of one arrayed waveguide grating connected by an arrayed waveguide, and the arrayed waveguide grating has an optical frequency relationship that couples with each other between the plurality of input waveguides and the plurality of output waveguides. In a predetermined optical signal processing circuit corresponding to the non-equal spacing channel frequency arrangement, the arrayed-waveguide grating has two cycles of the input waveguides with one cycle of the channel frequency of the input optical signal. And the output waveguide, the processing means is connected between the output waveguide of the first cycle and the output waveguide of the corresponding second cycle, and the processing means is connected between the output waveguide of the second cycle and the output waveguide of the second cycle. One input waveguide in the first cycle is set as an input port for an input optical signal, and a corresponding input waveguide in the second cycle is set as an output port.

The arrayed waveguide grating used in the present invention is a patent application filed by the same applicant as the present application, Japanese Patent Application No. 7-18237.
(Unpublished at the time of filing of the present application), the optical frequency relationship for coupling between the input waveguide and the output waveguide in the first period is set in the same manner as in the conventional arrayed waveguide grating. It has a structure in which an input waveguide and an output waveguide in the second period, which are coupled in the same optical frequency relationship, are further provided.

The optical signal processing circuit of the present invention can be used as an optical add / drop circuit by using an optical path switching means for branching or inserting an optical signal as the processing means.
Further, as the processing means, an optical attenuator is used to provide an optical amplifier and other gain equalizers, a dispersion compensation element is used to provide a dispersion equalizer for optical frequency multiplexed signals, and an optical delay element is used to provide a delay adjustment circuit and a wavelength. By using the conversion element, it can be used as a wavelength conversion circuit for the signal light multiplexed in optical frequency.

[0014]

The input / output ports of the arrayed waveguide grating are arranged for two cycles with the unequal channel spacing as one cycle, and the optical frequency division multiplexed signal is input to the input waveguide of the first cycle, The output of the output waveguide is input to the output waveguide of the second cycle, and an output optical signal is obtained from the input waveguide of the second cycle. Therefore, there is no crosstalk due to re-input to the input waveguide, and arbitrary unequal channel arrangement is possible.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of the present invention.
An example in which the present invention is applied to an optical add / drop circuit is shown. Here, a case where the number of channels N = 8 will be described as an example.

This optical add / drop circuit comprises an arrayed waveguide grating 1
0, the arrayed waveguide grating 10 has a structure in which two fan-shaped slab waveguides 12 and 14 are connected by an arrayed waveguide 13, and a plurality of input waveguides 11 and a plurality of output waveguides 15 are provided. The relationship between the optical frequencies of the input optical signals to be coupled to each other is predetermined corresponding to the channel frequency arrangement of the input optical signals which is not equidistant, and the input optical signals can be demultiplexed and multiplexed for each wavelength. The arrayed-waveguide grating 10 used in the present embodiment is provided with two periods, that is, 16 input waveguides 11 and output waveguides 15, where the channel frequency of the input optical signal is one period, and the input ports I and I are respectively provided. _{1 to} I ₁₆ and O _{1 to} O ₁₆ are formed. 2 × 2 each is provided between the output port O _i (i = 1, 2, ..., N) of the first cycle and the corresponding output port O _{i + N} of the second cycle.
The optical switch 30 is connected to the input port I ₁ of the first round.
One of the I ₈ input ports I _j (j = 1, ...,
8), in this example, j = 4 is set to the input port of the input optical signal, and the corresponding input port I _{j + N} of the second cycle is set to the output port.

2 connected between output ports O _i and O _{i + N}
The × 2 optical switch 30 has one input S connected to the output port O _i.
W-in1 is connected, and the other input SW-in2 is connected to an insertion port (not shown) to which an insertion optical signal is input. Also, the output port O of the arrayed waveguide grating 10
One output SW-out1 is connected to _{i + N,} and the other output SW-out2 is connected to a branch port (not shown) that outputs a branch optical signal. The connection states that the 2 × 2 optical switch 30 can take are the input SW-in1 and the output SW-out1, and the input SW-in2 and the output SW-out.
2 is connected to the bar state, input SW-in1 and output S
W-out2, input SW-in2 and output SW-out1
Are in a cross state in which is connected.

The optical signal input to the input port I ₄ is demultiplexed by the arrayed waveguide grating 10 and output to the output ports O _{1 to} O ₈ of the first cycle corresponding to each wavelength. The optical signal output from the output port O _i corresponds to the i-th 2 ×
If the two-optical switch 30 is in the bar state, it is directly returned to the corresponding output port O _{i + N} , and if it is in the cross state, it is output to the branch port. In the crossed state, if an optical signal is input from the insertion port, the optical signal enters the output port O _{i + N} of the optical waveguide grating 10. The optical signals that have entered the output ports O _{9 to} O ₁₆ have the same input / output waveguide arrangement, that is, port arrangement in the first period and the second period. It is output from I ₁₂ .

It is not necessary to provide the 2 × 2 optical switch 20 at each output port of the arrayed-waveguide grating 10, and it can be omitted for channels that do not require dropping and adding. The same applies to the case where branching or insertion is performed constantly.
Furthermore, by connecting an optical attenuator instead of the 2 × 2 optical switch 30, it can be used as an optical amplifier or other gain equalizer. Similarly, by connecting a dispersion compensation element, it can be used as a dispersion equalizer for frequency-multiplexed signals, by connecting an optical delay element, it can be used as a delay adjustment circuit, and by connecting a wavelength conversion element. It can also be used as a wavelength conversion circuit for optical frequency-multiplexed signal light.

[0020]

As described above, the optical signal processing circuit according to the present invention can process an arbitrary optical signal with respect to an optical frequency division multiplexed signal having unequal channels arranged without crosstalk between channels. effective.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a conventional example.

[Explanation of symbols]

 10, 20 Array waveguide grating 11, 21 Input waveguide 12, 14, 22, 24 Slab waveguide 13, 23 Array waveguide 15, 25 Output waveguide 30 2 × 2 optical switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhito Okamoto 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A means for demultiplexing an input optical signal in which channel frequencies are multiplexed at unequal intervals by wavelength, a plurality of processing means for processing each demultiplexed optical signal, and a plurality of these processings. Means for recombining the optical signals respectively processed by the means, wherein the demultiplexing means and the demultiplexing means are one arrayed waveguide in which two fan-shaped slab waveguides are connected by an arrayed waveguide. This arrayed waveguide grating has an optical frequency relationship that couples with each other between a plurality of input waveguides and a plurality of output waveguides, and corresponds to an unequal-spaced channel frequency arrangement of the input optical signals. In the predetermined optical signal processing circuit, the arrayed waveguide grating is provided with an input waveguide and an output waveguide for two cycles, where the arrangement of the channel frequencies of the input optical signal is one cycle. The processing means is connected between the output waveguide of the first cycle and the output waveguide of the corresponding second cycle, and one of the input waveguides of the two cycles 2. The optical signal processing circuit, wherein the input waveguide is set to the input port of the input optical signal, and the corresponding input waveguide of the second cycle is set to the output port. 2. The optical signal processing circuit according to claim 1, wherein the processing means includes an optical path switching means for branching or inserting an optical signal.