KR0175355B1 - Integrated Multiwavelength Channel Pass Filter - Google Patents

Abstract

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to the separation of a multi-channel channel signal with the stabilization and standardization of a wavelength (or frequency) of a multi-wavelength (or frequency) channel in a wavelength (or frequency) division multiple capacity optical communication. Possible multi-wavelength optical filter schemes are proposed.

Multiple loops form a Bragg grating with different wavelength selectivity in the center of each loop of the Sagnac loop connected by a 1xN optical splitter or a splitter of combiner to form a multiwavelength channel transmissive optical filter. A composition was proposed.

Thermal expansion, tension, and shrinkage is added to one side of the breg grating and the loop to change the wavelength selectivity of each breg grating and to adjust the phase of the optical signal that is reversed in the Shagnac loop. In addition, it has been proposed to use a silica material, an organic material, a semiconductor material, or the like to construct the entire composition of the optical fiber, the optical fiber coupler, or the like in a planar manner.

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to wavelength stabilizing or frequency standard elements of an optical source or to noise cancellation in wavelength (or frequency) division multiple optical communication using multiple wavelengths (or frequencies). It can be used as a device, and can be applied as a multi-wavelength (or frequency) channel drop device in an optical network.

Description

Integrated Multiwavelength Channel Pass Filter

1 is a structural diagram of an integrated multi-wavelength channel pass filter according to the present invention.

2 is a structural diagram of a single wavelength pass-type optical fiber filter of a conventional Bragg grating.

3 is a structural diagram of a multi-channel separation element using a waveguide grating arrangement using a conventional light coherence.

4 is an operation diagram of a multi-wavelength separation element using a conventional lattice.

* Explanation of symbols for main parts of the drawings

1: optocoupler 2: Bregg grating

3: optical fiber or optical waveguide 3 ': optical fiber

4: 1xN optical splitter or optocoupler 5: electrode

6: electric heater or PZT translator

6 ': electric heater 7: optical waveguide

8: N × N optical coupler 9: diffraction grating

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated multi-wavelength channel pass filter, and more particularly to stabilizing and normalizing the wavelength (or frequency) of a multi-wavelength (or frequency) channel in wavelength (or frequency) division multiple bulk optical communications. The present invention relates to a multi-wavelength filter that can be applied for separation and can be easily integrated for practical use. Wavelength (or Frequency) Division In multi-capacity optical communications, the stabilization and standardization of the wavelength (or frequency) of several wavelength (or frequency) channels is required, and it is also important to secure devices that separate these multi-wavelength channel signals.

In the future, in the high-density wavelength division multiple optical communication, in order to minimize crosstalk or interference between channels due to optical nonlinear effects induced by various wavelength channels, a composition in which frequency intervals between channels are not constant is required (IEEE Photonics Technology Letters, vol. .6, 754-756, 1994).

In the optical communication of such a multi-wavelength channel, a method using several existing optical filters for a single wavelength may be attempted, but this method is bulky and is not effective for system configuration.

Various optical filters have been studied in the past, and single-wavelength optical filters include optical filters in which bulky optical fibers are combined, or optical fiber Bragg gratings made by irradiation of an ultraviolet laser light source with optical fibers. grating filter (FIG. 2).

An optical filter capable of simultaneously separating multiple wavelength (or frequency) channels includes an interferometer type optical filter (FIG. 3) and reflection using an arrayed-waveguide grating arranged on a silica wafer. There is an optical filter (FIG. 4) having a structure in which each of the different wavelength signals diffracted in the diffraction grating or the transmission diffraction grating is separated into spatial arrangements of optical fibers or optical waveguides.

Multiwavelength silica waveguide interferometer filters have been developed in recent years. However, these filters are rather difficult to separate at a predetermined wavelength (or frequency) interval and to selectively extract desired channels.

FIG. 2 is a structural diagram of a single wavelength transmission optical filter using a conventional Bragg grating 2, an optocoupler 1, and an optical fiber chagnac loop 3 '.

As shown in FIG. 2, this filter is composed only of an optical fiber element, and has a single wavelength characteristic due to a single loop and has no disadvantage of wavelength variable characteristic (OOOC '89 Technical Digest, vol. 4, 64- 65, 1989).

3 is a structural diagram of an interferometer type multiwavelength optical filter using an arrayed-waveguide grating arranged on a conventional silica wafer.

As shown in FIG. 3, the filter has an interferometer composition in which loops 7 extending in length by ΔL are connected to two N × N star couplers 8. Since separation characteristics occur only at constant wavelength (or frequency) intervals, they also have some disadvantageous characteristics in the above-described high density wavelength (or frequency) division multiplexing optical communication.

The filter has the ability to separate multiple wavelength (or frequency) signals, but does not separate multiple wavelength channels simultaneously (Electronics Letters, vol. 30, 642-643, 1994).

4 is an optical filter structure diagram of a structure in which each of the different wavelength signals diffracted in the conventional diffraction grating 9 is separated into spatial arrangements of optical fibers or optical waveguides.

As shown in FIG. 4, the filter has a very sensitive position of an optical fiber or an optical waveguide that receives each wavelength channel to be diffracted in the diffraction grating, making the filter very difficult and in addition, coupling efficiency of the optical signal. Very low is the biggest disadvantage.

In addition, this filter has the function of separating the multiple wavelength (or frequency) signal separately as shown in Fig. 3, but there is no function of simultaneously separating the multiple wavelength channels.

Accordingly, an object of the present invention is to provide an optical waveguide filter which can selectively separate channel signals of various wavelengths and which can be easily integrated.

In order to achieve the object described above, the present invention provides an optical coupler, two 1 × N optical splitters connected through the optical coupler and an optical waveguide loop, and N optical fiber loops connecting the two 1 × N optical splitters. Chagnac loop consisting of; And a breg grating formed at a central point of the optical fiber loop and reflecting an optical signal by a wavelength characteristic determined according to the grating structure.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

1 is a structural diagram of a multi-wavelength channel pass optical filter according to the present invention, where 1 is an optical coupler, 2 is a Bragg grating, 3 is an optical fiber or an optical waveguide, 4 is a 1xN optical splitter or an optical coupler, 5 is an electrode, and 6 is an electrode. An electric heater or a piezoelectric element (PZT translator) is shown, respectively.

As shown in FIG. 1, the optical filter according to the present invention includes two 1 × N splitters of combiner 4 in an optical waveguide loop composed of one optical coupler 1. And a Sagnac loop structure in which several (or N) loops 3 are connected to the 1 × N optical splitter again.

At the central point of each of these loops, a Bragg grating 2 is formed and a wavelength filter determined according to the lattice structure is used to construct an optical filter that exhibits wavelength characteristics for several wavelengths as a whole. There is a number. The optical signals traveling in the opposite directions in the optocoupler 1 are reflected as wavelength signals determined in each Bragg grating, so that only the wavelength signals are transmitted back from the optocoupler 1, resulting in a bra The multi-channel channel pass filter function is determined according to the wavelength characteristics of the gratings 2.

Here, a fine adjustment function is required so that the optical signal reflected from each Breg grating 2 returns to have the same phase in the optical coupler 1, and for this function, the optical path is formed by thermal expansion or tension on one side of the loop. An electric heater or a piezo-electric expansion element 6 with an electrode 5 was added to enable electrical adjustment so that the change could be made.

In addition, in order to finely adjust the wavelength characteristics of each Bragg grating 2, a composition for attaching a heater or a piezoelectric expansion element 6 to the grating is proposed to change the periodic interval of the grating.

The optical filter of the present invention forms a breg grating in accordance with the desired wavelength characteristics in advance in manufacturing, and if necessary, the reaction wavelength characteristics can be finely adjusted by an electric heater or a piezoelectric expansion element attached to each breg grating. It is characterized by the fact that it can be easily formed as a multiwavelength filter structure responsive to the channel.

In addition, the entire composition can be configured as an optical fiber and an optical fiber element, and has the advantage that it can be formed as an optical waveguide on a two-dimensional plane by using an organic material or a material such as silica or a semiconductor.

As described above, the present invention makes it easier to select any of several channel wavelengths and makes it possible to cleanly select optical signals of transmission wavelengths, as compared to conventional Mach-Zehnder Interferometer Type flat integrated optical filters. It has the effect that the fine adjustment of the selected wavelength is easy.

In the future, the present invention is expected to be utilized as a wavelength division demultiplexer, a reference wavelength element of channel wavelengths, and a multi-channel optical signal separation element in a large-capacity wavelength division multiple optical communication.

Claims (2)

A shagnac loop comprising an optical coupler, two 1 × N optical splitters connected through the optical coupler and an optical waveguide loop, and N optical fiber loops connecting the two 1 × N optical splitters; And a Bregg grating formed at a central point of the optical fiber loop and reflecting an optical signal by a wavelength characteristic determined according to the grating structure. The electrode of claim 1, wherein the optical path is electrically changed on one side of the optical fiber loop in order to finely adjust the optical signal reflected from the Bregg grating to have the same phase in the optical coupler. Integrated multi-wavelength channel pass optical filter, characterized in that the electric heater is added, using a two-dimensional planar optical waveguide using one selected from the group consisting of organic matter, silica, semiconductor instead of the optical fiber loop Integrated multi-wavelength channel pass optical filter, characterized in that.