JP2001091760A - Wavelength variable optical part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems of tunable wavelength variable optical parts having a grating structure using glass fibers that the parts generate extremely small displacement when tension is applied, and that when large displacement is to be generated, the device is made large in size or the fiber is broken. SOLUTION: The wavelength variable optical parts have an assembled structure of a grating optical waveguide made of a polymer material and a piezoactuator which add tension to the waveguide. By this method, large displacement is obtained with small tension, and the structure of the part itself is simple and is easily produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tunable wavelength-variable optical component used in a wavelength-variable light source and a wavelength-variable filter in the field of optical communication such as a wavelength division multiplexing optical communication (WDM) system. The present invention relates to a wavelength tunable optical component using a polymer optical waveguide having

[0002]

2. Description of the Related Art In a WDM transmission system, a signal is transmitted through a plurality of lights having different wavelengths in one optical fiber, and the capacity of optical communication can be increased. Recently, a maximum of 800 wavelengths are multiplexed on one optical fiber,
Some products have increased transmission speeds up to terabits / second.
In order to use a necessary signal from an optical fiber through which such a signal flows, a technique for multiplexing or demultiplexing only an optical signal having a single wavelength is required. In WDM, for example, 1.55μ
At a wavelength in the m band, a frequency interval of 200 GHz, 4 to 8
Channel multiplexing, frequency interval 100 GHz, 16-4
A system called zero-channel multiplexing is generally used. Since these wavelength intervals correspond to 1.6 nm and 0.8 nm, respectively, a specific wavelength (channel) is multiplexed or demultiplexed from such a wavelength signal. For this purpose, a high-Q value wavelength filter having a transmission band sufficiently narrower than this interval is required.

One of such narrow-band, high-Q-wavelength filters uses a fiber Bragg grating (FBG) technique. FBG is a technique in which a refractive index modulation grating is formed by irradiating an ultraviolet ray in an optical fiber. The FBG is a technique in which a target wavelength is reflected by the grating and is combined with an externally provided optical coupler or optical circulator to separate light. However, most of the wavelength filters using the FBG technology that are currently in practical use can only be applied to a certain narrow-band wavelength. Therefore, in order to separate several types of multiplexed wavelengths, it is necessary to select a selected wavelength. You need as many filters as there are. Therefore, in recent years, there has been an increasing demand for a wavelength-variable filter capable of separating all wavelengths multiplexed in a certain wavelength band. As a tunable wavelength-variable optical component, a component using FBG is currently being studied most.
The diffraction grating has wavelength selectivity such that only a specific wavelength (Bragg wavelength) determined by the grating period and the effective refractive index in the waveguide for guided light is reflected, and other wavelengths are transmitted. By changing any of the effective refractive indexes in the waveguide, the reflection center wavelength can be changed.

As a specific method of changing the Bragg wavelength of the FBG, a method of changing the effective refractive index and the period by thermal expansion due to a change in the temperature of the grating portion, a method of expanding and contracting the grating portion by applying mechanical tension to set the period. A changing method or the like is used. Of these, in the method of changing the temperature of the grating portion, the temperature change of the linear expansion coefficient of quartz, which is the main material of the fiber, is small,
Further, since the change in the refractive index is small, the change in the 1.55 μm wavelength band is both reported to be as small as about 1.2 × 10 ⁻² nm / deg. It requires time for stabilization, and it is difficult to adapt to high-speed optical switching or the like by changing the wavelength. In addition, as a method of changing the period of the grating portion by applying mechanical tension, both ends of the grating portion of the FBG are fixed to a moving stage using a piezoelectric element or a cylindrical piezoelectric actuator, and the optical axis of the optical fiber is fixed. A method of applying a tension or a compressive force in a direction has been common.

[0005]

SUMMARY OF THE INVENTION However, FBGs
The quartz glass fiber material, which is the main raw material, has a very small displacement with respect to the application of tension, and if a large displacement is to be obtained, a high voltage of 100 V or more must be applied to the driving piezo element, and the device becomes large. And problems such as troublesome handling. Further, fixing and pulling the fiber at two points causes a large tension to be applied to the fixed portion, which may cause a problem that the fiber is cut. Therefore, the present invention solves these inconveniences of the prior art, and provides a small and simple wavelength tunable optical component that can easily change the Bragg wavelength with a low voltage drive even when a tension is applied by a piezo element. It is in.

[0006]

Means for Solving the Problems To solve the above-mentioned problems, the present inventor has developed a structure in which a grating optical waveguide made of a polymer material having high elasticity and a piezo actuator for applying tension to the grating optical waveguide are combined. Wavelength tunable optical components. By configuring the grating portion of the optical waveguide with a polymer material, a large displacement can be obtained with a small tension as compared with a conventional fiber grating, and further, the polymer optical waveguide is easily integrated with a piezo actuator. In addition, since the change in the piezo actuator is efficiently transmitted to the grating portion, the structure of the component itself is simple and can be easily manufactured, and a small-sized wavelength-variable optical component driven at low voltage can be realized.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a grating for a polymer optical waveguide used in a wavelength tunable optical component of the present invention, both a relief type and a refractive index modulation type can be used. 1A and 1B are explanatory views of a relief type optical waveguide grating structure, in which FIG. 1A is a perspective view, and FIG. 1B is a cross-sectional view along the core longitudinal direction. In FIG. 1, 10 is a relief type optical waveguide, 1 is a relief type grating, 2 is a core, 3 is a clad, and 4 is a substrate of a relief type optical waveguide. The method for producing the relief type optical waveguide shown in FIG. 1 is not particularly limited, and follows the process for producing a normal buried channel waveguide by core ridge processing by thin film deposition by spin coating, photolithography, etching or the like. A clad 3 is formed on a substrate 4 and a core 2 is deposited thereon.

After the core 2 is deposited or the core ridge is formed, a resist is applied to the relief type grating 1, a grating pattern is written by two-beam interference exposure, phase mask exposure, electron beam drawing, etc., and development and etching steps are performed. It can be manufactured with. When a photopolymer is used as the material of the core 2, it is possible to write directly on the core without using a resist. In recent years, a technique of manufacturing a polymer optical waveguide grating using a structure manufactured by using a micromachining technique such as an electron beam lithography apparatus as a mold has also been reported. As the polymer material, any material can be used as long as it can produce a thin film and is stable in a controlled temperature range. As an example, an acrylic polymer, a silicone resin, a UV curable resin, or the like can be used. After fabrication of the grating, the cladding 3 is formed on the upper surface to complete the grating.

FIGS. 2A and 2B are explanatory views of the refractive index modulation type optical waveguide grating structure. FIG. 2A is a perspective view, and FIG. 2B is a cross-sectional view along the longitudinal direction of the core. In FIG. 2, reference numeral 20 denotes a refractive index modulation type optical waveguide, 5 denotes a refractive index modulation type grating, 6 denotes a core, 7 denotes a clad, and 8 denotes a substrate of the refractive index modulation type optical waveguide. In the method of manufacturing a refractive modulation type optical waveguide, a cladding 7 is formed on a substrate 8 of the refractive index modulation type optical waveguide, a core 6 is deposited thereon, and a cladding 7 is further formed thereon. The core 6 can be manufactured by writing a grating pattern as a refractive index change by two-beam interference exposure, phase mask exposure, electron beam drawing, or the like, using a material whose refractive index changes by light or electron beam irradiation. As an example, the refractive index of an acrylic polymer is increased by electron beam irradiation, and the refractive index of a benzene ring-containing silicone polymer is decreased by UV irradiation. Therefore, the acrylic polymer can be used for manufacturing a refractive index modulation type grating.

FIGS. 3A and 3B are views for explaining the configuration of an embodiment of the wavelength tunable optical component of the present invention. FIG. 3A is a perspective view, and FIG. 3B is a cross-sectional view along the longitudinal direction of the core. 3, reference numeral 10 denotes a polymer optical waveguide having the relief type optical waveguide grating structure shown in FIG. Reference numeral 9 denotes a piezo element on the substrate of the polymer optical waveguide. Reference numeral 14 denotes a voltage source applied to the piezo element. In the embodiment shown in FIG. 3, a piezo element 9 is used for the substrate of the polymer optical waveguide having the grating structure shown in FIG. 1, and a voltage is applied to the piezo element 9 by a voltage source 14 to make the substrate a piezo actuator. Things. The piezo actuator is connected to the piezo element 9,
This utilizes the property that when an electric field is applied by the applied voltage source 14, the shape changes according to the strength. The material of the piezo element 9 is lead zirconate titanate (PZ).
T), and many products are already on sale. A vertical effect type piezoelectric element is used as the piezo element.

The longitudinal effect type piezoelectric element applies an electric field in the direction of displacement. In order to prevent the applied voltage from becoming excessively high,
In many cases, a multilayer structure is formed by the same manufacturing method as a ceramic capacitor, and because of its excellent driving force and responsiveness, it is used for positioning a diamond cutting edge of a precision lathe or driving a needle of a scanning tunneling microscope. The actual amount of displacement of the longitudinal effect type piezoelectric element depends on the number of piezo material layers constituting the actuator, the piezo material itself, and the voltage supplied to each layer, but the power consumption is low and a certain load was applied. Holding a position consumes very little energy.

The polymer optical waveguide 10 having the grating structure is formed on the substrate of the piezo element 9 in a direction in which the grating structure of the polymer optical waveguide 10 coincides with the extension direction by applying a voltage to the piezo element. In the configuration of FIG. 3, the substrate 4 of the polymer optical waveguide 10 shown in FIG.
Since the substrate 4 itself is a stretchable substrate because the structure is replaced with the piezo element 9, the polymer optical waveguide formed on the substrate 4 expands and contracts integrally with the substrate. By controlling the voltage, the grating period can be changed.

In the embodiment shown in FIG. 3, the wavelength tunable optical component using a piezo element as the substrate 4 of the polymer optical waveguide 10 having the relief type optical waveguide grating structure shown in FIG. 1 has been described. A wavelength tunable optical component having the same function even when a piezo element is used for the substrate 8 of the polymer optical waveguide 20 having the refractive index modulation type optical waveguide grating structure shown in FIG. Can be realized. Further, in the embodiment of FIG. 3 described above, the method of manufacturing the polymer optical waveguide 10 directly on the substrate 9 of the piezo element has been described. It is possible to realize a wavelength tunable optical component having the same function as a configuration in which the component is bonded to a substrate.

FIG. 4 is a view for explaining the configuration of another embodiment of the wavelength tunable optical component of the present invention, and is a sectional view along the longitudinal direction of the core. 4, reference numeral 10 denotes a polymer optical waveguide having the grating structure shown in FIG. Reference numerals 9 and 15 indicate piezo elements, and reference numeral 14 indicates a voltage source applied to the piezo elements 9 and 15. Polymer optical waveguide 10 having grating structure
Is formed on the substrate of the piezo element 9 in the direction in which the grating structure of the polymer optical waveguide 10 matches the direction of extension by the applied voltage 14 of the piezo element, as in FIG.
Further, a piezo actuator 15 is formed on the upper surface of the polymer optical waveguide 10 in a direction in which the polymer optical waveguide 10 grating structure coincides with the extension direction by applying a voltage to the piezo actuator.

The embodiment of FIG. 4 has a structure in which the substrate 4 of the polymer optical waveguide shown in FIG. 1 is replaced with the substrate 9 of the piezo element, and a piezo element 15 similar to the substrate is provided on the upper surface thereof. Therefore, the polymer optical waveguide expands and contracts integrally with the substrate 9 and the piezo element 15, and it is possible to more efficiently change the grating period by voltage control. In the embodiment of FIG. 4, the wavelength tunable optical component using a piezo element as the substrate 4 of the polymer optical waveguide 10 having the relief type optical waveguide grating structure shown in FIG. 1 has been described. Change to 10 and Figure 2
Even if a piezo element is used for the substrate 8 of the polymer optical waveguide 20 having the refractive index modulation type optical waveguide grating structure shown in (1), a wavelength tunable optical component having the same function can be realized. Also in the embodiment of FIG. 4 described above, it is possible to realize a wavelength tunable optical component having the same function even when the polymer optical waveguide 10 is independently manufactured and a piezo element substrate is bonded to both surfaces thereof. Is possible.

[0016]

As is apparent from the above description, the wavelength tunable optical component of the present invention is a combination of a grating optical waveguide made of a polymer material having high elasticity and a piezo actuator for applying a tension to the grating optical waveguide. A wavelength tunable optical component having a different structure can be realized. Because of this, it is possible to have a structure in which a polymer optical waveguide having a grating structure and a piezo actuator used to apply tension to the grating structure are integrated.
Since it is smaller than conventional products and has a very simple structure, an inexpensive and simple device can be provided. Also, since the expansion rate of the piezo becomes the rate of change of the grating period as it is, it is possible to switch the wavelength at a higher speed than in the conventional technology. The application of semiconductor lasers to external resonators can be widely expected.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a relief type optical waveguide grating structure.

FIG. 2 is an explanatory diagram of a refractive index modulation type optical waveguide grating structure.

FIG. 3 is a diagram illustrating a configuration of an embodiment of a wavelength tunable optical component of the present invention.

FIG. 4 is a diagram illustrating a configuration of another embodiment of the wavelength tunable optical component of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Relief type grating 2 ... Relief type grating core 3 ... Relief type grating clad 4 ... Relief type optical waveguide substrate 10 ... Relief type optical waveguide 5 ... Refractive index modulation type Grating 6 ... refractive index modulation type grating core 7 ... cladding of refractive index modulation type grating 8 ... substrate of refractive index modulation type optical waveguide 20 ... refractive index modulation type optical waveguide 9, 15 ... Piezo element 14 ... Voltage source of piezo element

Continued on the front page (72) Inventor Asuka Yamamori 1382-1 Shino Otsu, Tobu-cho, Tobu-cho, Nagano-gun, Japan BA07 CA05 DA02

Claims (8)

[Claims] 1. A polymer optical waveguide having a grating structure in a core portion, and a piezo element substrate for applying a mechanical tension to the polymer optical waveguide, wherein the piezo element substrate mechanically converts the polymer optical waveguide into a grating structure. A wavelength tunable optical component that varies the grating period of the polymer optical waveguide by applying tension to the optical waveguide. 2. A wavelength tunable optical component according to claim 1, wherein a polymer optical waveguide to which tension is applied on a piezo element substrate to which tension is applied has an integrated structure. Optical components. 3. The wavelength tunable optical component according to claim 1, wherein a relief type grating is used as the grating of the polymer optical waveguide. 4. The wavelength tunable optical component according to claim 1, wherein a refractive index modulation type grating is used as the grating of the polymer optical waveguide. 5. A tension to a polymer optical waveguide having a sandwich structure in which a polymer optical waveguide having a grating structure in a core portion and a piezo element substrate for applying mechanical tension to both surfaces of the polymer optical waveguide with the polymer optical waveguide interposed therebetween is provided. A wavelength tunable optical component comprising: an application means; and applying a tension to the grating structure of the polymer optical waveguide by a tension applying means, thereby changing a grating period of the polymer optical waveguide to tune the wavelength. 6. The wavelength tunable optical component according to claim 5, wherein a polymer optical waveguide to which tension is applied is integrally formed on the piezo element substrate of the tension applying means. Variable optical components. 7. The tunable optical component according to claim 5, wherein a relief-type grating is used as the grating of the polymer optical waveguide. 8. The wavelength tunable optical component according to claim 5, wherein a refractive index modulation type grating is used as the grating of the polymer optical waveguide.