JP2003504659A - Optical coupling - Google Patents

Abstract

(57) Abstract: In a method and apparatus for coupling light to / from an optical waveguide, a local resonance for a specific wavelength is formed in a portion of the waveguide intended to couple a specific wavelength component of light. Is done. Optical coupling into and out of the waveguide occurs at those parts that resonate locally.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION

  The present invention relates to methods and apparatus for coupling light into / from an optical waveguide.

[0002]

[Prior art]

Light guiding in optical waveguides, and in particular in optical fibers, is a well-known technique for carrying energy and information in the form of light. For example, as in the case of optical fibers, one-dimensional optical waveguides are based on optical waveguides in cylindrically symmetric media. Optical waveguide is performed by a medium having a low refractive index, that is, a core surrounded by a so-called cladding, and optical waveguide by a simple model is obtained by repeating total reflection between the core and the cladding. However, light can only propagate in certain defined directions (so-called modes) defined by certain phase conditions that must be met in connection with the propagation of light. According to the standard model, these modes consist of eigensolutions of Maxwell's equations with existing cylindrical boundary conditions.

If the cross-sectional dimensions of the core are small enough, light can only propagate in a single aforementioned mode. An optical waveguide having this characteristic is called a monomode optical waveguide. Monomode waveguides have certain important advantages over waveguides that allow multiple modes (multimode waveguides). For example, the information carrying capacity of monomode optical fibers (often referred to as single mode optical fibers) is much greater than that of multimode fibers when light is guided through long fibers. Another important advantage of monomode waveguides, such as single mode fiber, is that there is no ambiguity. Apart from the polarization state of the light, the properties of the light become clear along the entire waveguide. Specifically, the light intensity distribution becomes clear along the entire waveguide. This is very important in making the operation of the waveguide-based component predictable. For the characteristics of single-mode fiber, see, for example, “Single-m by LB Jeunhomme.
ode fiber optics: Principles and applications '' (Marcel Dekker, New York
(1990)).

Generally, in order to increase the transmission capacity of an optical waveguide, a plurality of different channels are used, each channel consisting of a particular optical wavelength. This technique is usually called wavelength division multiplexing or WDM (wavelength division multiplexing). For an overview of WDM technology, see "A review of WDM technology and applications" by GE Keiser (Opt. Fiber Technol,
5, pp. 3-39, (1999)). In connection with WDM, it is desirable to be able to add and remove a single channel, ie a single optical wavelength, to the waveguide.

A well-known technique for wavelength-selectively changing the propagation direction of light utilizes optical phase gratings. The optical phase diffraction grating is a structure in which the refractive index basically changes periodically in an optically transparent medium. This technology is described, for example, in "Diffraction gratings" by MC Hutley (Academic Press,
London (1982)). When light enters the optical phase diffraction grating, a small part of the incident light is reflected by each diffraction grating element (period). When a plurality of diffraction grating elements are arranged in series (ie arranged in a phase diffraction grating), the total amount of reflected light is the sum of all these separate reflections. The portion of the incident light reflected by each diffraction grating element depends on the depth (amplitude) of the refractive index modulation of the phase diffraction grating, that is, the difference in the refractive index of the diffraction grating element. The greater the modulation, the greater the portion of the incident light reflected by each phase element. If the propagation direction of the light incident on the phase diffraction grating is basically perpendicular to the diffraction grating, that is, the normal to the diffraction grating element, the diffraction grating is said to be operating in the Bragg domain. Called. As a result of normal incidence, light is reflected essentially parallel to the direction of incidence (ie in the opposite direction of propagation). In this way, the light reflected by each diffraction grating element overlaps with the light reflected by all other diffraction grating elements and causes interference. In a monomode waveguide, all reflections within the cone of a given angle are coupled into the only mode (propagation direction) allowed by the waveguide. For wavelengths where these reflections are in phase, constructive interferenc
e) occurs and each grating element only gives a low intensity reflection, but considerable reflection is obtained for this wavelength from the entire grating. This wavelength at which significant reflection is obtained from the entire grating is called the Bragg wavelength λ _bragg and is given (for normal incidence) by λ _bragg = 2nΛ. Here, n is the average value of the refractive index, and Λ is the period of the phase diffraction grating. The reflectance for the Bragg wavelength is given by R _bragg = tanh ² κL. Here, L is the length of the Bragg diffraction grating in the light propagation direction, and κ
Is

[Equation 1] Is defined by Here, Δn is the amplitude of the refractive index modulation. Since the refractive index modulation Δn is usually small (10 ⁻⁵ to 10 ⁻³ ), it can be seen that the reflectivity equation can be expanded to a power series, whereby the reflectivity is approximately proportional to the square of Δn.

When the incident angle of light on the phase diffraction grating is not vertical, that is, when the diffraction grating surface is tilted, the light is not reflected in the incident direction. Therefore, the light reflected by each grating element only partially overlaps the light reflected by the other grating elements, which makes the interference effects less noticeable than in the Bragg domain.

A method of providing a phase diffraction grating in an optical waveguide is disclosed in, for example, Glenn et al., US Pat.
You can see from 5,110. According to this method, the waveguide is illuminated by ultraviolet light through an interferometer, which results in a periodic illumination of the waveguide, which results in a periodic change in the refractive index in the waveguide. This change in refractive index remains in the waveguide even after irradiation. By controlling the angle between the interfering UV rays, so that the desired Bragg wavelength is obtained,
You can select the cycle. Since the diffraction grating element whose surface is oriented at right angles to the propagation axis of the waveguide is provided, the incident angle of the interfering ultraviolet rays is usually arranged symmetrically with respect to the propagation axis of the waveguide. Selected so that the grating operates in the Bragg domain. In this technology, the waveguide structure is germanium silicate (germ
It has been found that a waveguide composed of anium silicate, i.e. a waveguide structure, is most effective for a waveguide composed of quartz to which a certain amount of germanium is added.

US Pat. No. 5,042,897 to Meltz et al. Describes a tilted (tilted) grating, that is, a grating element whose plane intersects the propagation direction of the waveguide at an angle other than 90 degrees ( A device for coupling light from a waveguide using a phase grating with a refractive index variation) is described. These tilted gratings are provided by orienting the interferometer at an angle with respect to the propagation axis of the waveguide as described above. The angle at which light is coupled from the waveguide is determined by the tilt angle of the diffraction grating element with respect to the propagation axis of the waveguide (
Horizontal phase matching condition) and wavelength (longitudinal phase matching condition). For example, R.
"Fiber Bragg Gratings" by Kashyap (Academic Press, London (1999))
Please refer to. The tilted grating element acts as a small, almost completely transparent mirror. The diameter of the mirror (diffraction grating element) is basically equal to the diameter of the waveguide structure. For example, in single mode fiber, the waveguide structure is composed of a core of fiber, which typically has a diameter of about 10 micrometers. Since this diameter is not so large compared to the wavelength of light, the mirror (diffraction grating element) causes diffraction of reflected light. As a result, the reflected light spreads conically around the angle defined by the tilt angle of the diffraction grating element. The lateral phase matching condition causes this angle to be approximately twice the tilt angle. Diffraction grating elements reflect light that partially overlaps, so the interference from a given wavelength builds up only when the light from each successive diffraction grating element is in phase with the light from the previous diffraction grating element. Cause This occurs at some fixed angle, which is the longitudinal phase matching condition.

[Equation 2] Given by. Here, N _eff and n _clad are the refractive indices of the waveguide structure (core) and the substrate (clad), respectively, and the substrate is assumed to have an infinite width in the above equation, and φ _L is the output coupling angle at the cladding and θ _g is the tilt angle.

A further development of the device with a tilted diffraction grating is described in Meltz et al., US Pat. No. 5,061,032. In this device, the period of the tilted grating is not constant, but rather varies along the propagation axis of the waveguide. For example, the period of the grating can increase or decrease linearly (or according to some other mathematical function) along the waveguide. Thus, a diffraction grating whose period changes monotonically is called a "chirped" diffraction grating (chirp = frequency sweep). Utilizing a customized chirp function allows outcoupling of a given wavelength to occur, providing a focal line that extends across the waveguide.

[0010]

[Problems to be Solved by the Invention]

In the above method of coupling light from a waveguide using a tilted grating, a substrate (
The output coupling angle is required to be sufficiently large in order to prevent the occurrence of total internal reflection between the clad) and the surrounding material (envelope). In a typical optical fiber, the output coupling angle φ _L
Must be greater than about 44 °, which requires the tilt angle θ _g to be at least about 22 °. For a given modulation (amplitude) of the grating, its efficiency decreases with increasing tilt angle. A further drawback is that the output coupling is extremely polarization dependent. One approach aimed at avoiding these drawbacks is described in US Pat. No. 5,832,156 by Strasser et al. According to this document, a prism having the same index of refraction as the cladding of the fiber can be utilized, the prism being brought into optical contact with the fiber using a contact liquid. This technique allows a tilt angle of less than 15 °, thereby avoiding the disadvantages to some extent. Prisms are also used for spatial separation of output coupling wavelengths using prism dispersion. However, there are some drawbacks to this output coupling. First, the chirp function serves its intended purpose only for certain wavelengths, thus limiting wavelength resolution. Secondly,
Due to the limited length of the chirped grating, considerable diffraction occurs for small tilt angles. Third, the coupling efficiency will be different for different wavelengths.

Accordingly, there is a need for improved apparatus and methods for coupling light into / from an optical waveguide that essentially avoids the aforementioned problems. The main object of the invention is to improve the feasibility of coupling light into / from an optical waveguide. This object is achieved by using an optical coupling device and method of the kind set forth in the appended claims. A particular object of the present invention is to provide a device for wavelength-selective optical coupling to / from an optical waveguide, which has a significantly higher spectral resolution than is possible with the prior art.

Another object of the present invention is to maintain the coupling efficiency so that, for example, a signal having a plurality of wavelength components propagating through an optical waveguide can be analyzed as a whole signal without affecting much. With respect to the prior art, it is to provide a device for optical coupling to / from an optical waveguide, which allows a weaker and more precise coupling mechanism. It is a further object of the present invention to provide a device for optical coupling to / from an optical waveguide that is easy to manufacture and mechanically robust.

[0013]

[Means for Solving the Problems]

The present invention is based on the insight that resonance in optical waveguides improves the feasibility of coupling light with respect to the waveguide. Since a specific wavelength component resonates in a specific part of the waveguide, not only a more efficient coupling of the resonant wavelength component is obtained, but also the concentration in the resonance part (local increase in power density) It is also spatially separated from the wavelength component of. To explain this another way, the coupling strength of a wavelength component is significantly increased in the portion of the waveguide that resonates with this wavelength component as it is coupled into and out of the waveguide. The wavelength components of the light propagating through the waveguide can be spatially separated by providing the waveguide with a plurality of resonance portions that resonate with specific wavelength components of the light. Resonance increases the coupling strength of a particular wavelength component at the corresponding resonant portion. Therefore, wavelength selectivity is achieved by spatially separating the resonant parts and by increasing the coupling efficiency of each wavelength component at the corresponding resonant part. As a result, the coupling of specific wavelength components to / from the waveguide can be very conveniently performed in the resonant part.

According to one aspect, the present invention enables outcoupling of a particular wavelength component from an optical waveguide in which multiple wavelength components are propagating, without significantly affecting uncoupled wavelength components. Wavelength-specific local resonances in the waveguide result in an increase in the local power density of the relevant wavelength components, so that in most applications, the effect on the wavelength component with the original power density is negligible. Allows the use of weak bonds.

According to another aspect, the invention enables the coupling of light to / from an optical waveguide, where different wavelength components are coupled to / from the waveguide at spatially separated portions. This could be the use of a detector matrix that extends along the waveguide to detect different waveguide components in the out-coupled light, or a light source that extends along the waveguide (eg a laser with different emission wavelengths). It has a number of very prominent advantages, such as the incoupling of different wavelength components using a matrix of. The present invention also provides for each waveguide component,
It also allows very smooth coupling to the associated connecting waveguide at the corresponding resonant part.

Therefore, a major advantage of the present invention is that different waveguide components can be coupled to / from an optical waveguide, such as an optical fiber, at different locations along the waveguide. Therefore, the device according to the present invention comprises at least one optical waveguide and means for coupling light to or from the optical waveguide, and means for providing the optical waveguide with a portion locally resonating to a specific waveguide component. It is provided. Further, the means for optically coupling the wavelength component to or from the waveguide structure is adapted to couple light at the resonant portion corresponding to the wavelength component.

According to a particularly preferred embodiment of the invention, the waveguide structure is a fiber core in an optical fiber (preferably a single mode optical fiber), with a local phase grating arranged in the fiber core to provide localized light. A resonant portion is provided. The essential feature is the modulation depth of the grating, namely the index amplitude (index
amplitude) is large enough to cause a resonance and thus a local increase in power density. The phase diffraction grating is preferably a Bragg diffraction grating with a monotonically increasing or decreasing period, a so-called chirp Bragg diffraction grating. Therefore, the Bragg wavelength is different in different parts of the grating,
As a result, the different wavelength components correspond to the Bragg wavelength at different parts of the grating. This means that the light, which is at least partially reflected by the diffraction grating in this part, fluctuates back and forth, so that the wavelength corresponding to the local Bragg wavelength causes the resonance and the power density increase locally. Means to indicate. Thereby, a plurality of spatially separated portions of the light propagating in the fiber core are obtained along the spread of the chirp diffraction grating and exhibit resonance to a predetermined wavelength component forming a part of the light. The deeper the refractive index modulation of the chirped diffraction grating, the more the respective wavelength components are concentrated in the corresponding resonance portion. Other objects and advantages of the invention will be apparent from the following detailed description of the preferred embodiments of the invention.

[0018]

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described in more detail by means of a plurality of preferred embodiments with reference to the accompanying drawings. In the drawings, similar or corresponding parts are designated by the same reference signs. As an introduction, the principle behind the first preferred embodiment of the present invention is shown in FIGS.
The prior art shown in FIG. 3 is used as a starting point and will be described with reference to FIGS.

According to this embodiment, an optical waveguide, for example a single mode optical fiber 1, is provided with a chirped Bragg diffraction grating 2. The diffraction grating 2 is manufactured by the prior art. Diffraction gratings are formed with a monotonically increasing or decreasing period, ie, chirped, so that different Bragg wavelengths are obtained at different portions along the grating. More specifically, the Bragg wavelength monotonically increases or decreases according to the period of the grating as a function of longitudinal position along the grating. For the sake of explanation, it is arbitrarily assumed that the light propagating in the waveguide is composed of three wavelength components λ1, λ2 and λ3, which are designated by the reference numerals 11, 12 and 13 in the drawing. Due to the chirped grating 1, the different wavelength components 11, 12, 13 match the Bragg wavelength of the grating at different parts 21, 22, 23 along the grating. A strong reflection is obtained for each wavelength component in these parts, as a result of which, for example, the wavelength component 11 is reflected by the chirp diffraction grating in the region indicated by reference numeral 21. However, the reflection is equally efficient in the case of light incident from the opposite direction, so that the reflected light is reflected again by the diffraction grating in said region 21. A resonance effect that locally increases the power density occurs for the wavelength component that matches the local Bragg wavelength in the region 21. Similarly, for the other wavelength components 12 and 13, resonance can be obtained at the resonance portions 22 and 23 of the corresponding diffraction grating. According to the invention, the purpose of increasing the power density in these resonant parts is to use wavelength-selective means in each part, using output coupling means arranged (or operatively connected) adjacent to the waveguide. That is, it is possible to couple light from the waveguide. The main advantage of the optical coupling according to the invention is that the coupling coefficient can be so weak that non-resonant (power density does not increase) wavelengths are essentially unaffected. Another major advantage is that because the resonant portion for each wavelength component is located at a different location along the grating, different wavelengths can be output coupled at different locations along the grating. Correspondingly,
The incoupling of light can be wavelength-selective, so that only wavelengths at which the grating resonates locally are coupled into the waveguide. FIG. 5 shows that said means for coupling light into / out of the optical waveguide has a phase grating (ie tilted) having grating elements whose planes intersect at an angle different from 90 ° with the propagation axis of the waveguide structure. 1 shows a first preferred embodiment of the present invention composed of a diffraction grating 3). This tilted diffraction grating
The chirp diffraction grating is formed so that the output coupling is negligible at the position and wavelength where it does not resonate. However, the regions 21, 22, 2 that resonate (increase the power density)
In 3, efficient binding is obtained. Since each wavelength component circulates in each part, light is coupled out in two directions 31ab, 32ab, 33ab. The outcoupling with a tilted grating is polarization dependent, so that in this case the outcoupling mainly occurs for one of the two polarization directions of the light.
Two tilted diffraction gratings can be conveniently placed in the waveguide structure, one diffraction grating being rotated 90 degrees about the propagation axis of the waveguide structure, and the output coupled light is separated by two. Obtained with four lobes (not shown) located opposite each other in the set. Thus, each of the opposite sets of lobes contains light of the same polarization.

FIG. 6 shows a second preferred embodiment of the present invention. In this case, the coupling means comprises a Bragg grating 4 having a refractive index modulation which decreases across the grating. Therefore, the amplitude (modulation depth) is at one end 41 of the diffraction grating and from the opposite end 42 (
Lower in the radial direction). This means that the light, when reflected by the diffraction grating, has a slightly different propagation direction than the incident direction. In this application, this type of grating is a transversally asymmetrical grating.
hase grating). If the lateral modulation depth variation is large enough, it is possible to couple light into and out of the waveguide using a laterally asymmetric phase grating. Preferably, as shown in the drawing, the chirped Bragg grating 2, that is, the means for providing local resonance (local increase in power density) and the lateral asymmetric phase grating 4 are
The same diffraction grating. The tilted diffraction grating described above can also be a laterally asymmetric phase diffraction grating, requiring less pronounced tilt to provide optical coupling to / from the optical fiber. This reduces the polarization dependence of the coupling, which is an advantage in some applications.

FIG. 7 shows a third preferred embodiment of the present invention. Similar to the previous embodiment, the local wavelength-specific resonances 21, 22, 23 are caused by the chirped phase grating 2 arranged in the waveguide 1. The optical waveguide is preferably an optical fiber, particularly preferably a single mode optical fiber. In this embodiment, said means for coupling light to / from an optical fiber comprises means 61, 62, 63 for evanescent coupling light to / from said fiber. Waveguide structure 5 (
The core) is arranged in the fiber such that the surrounding cladding 6 is thin enough to allow evanescent coupling to / from the fiber core 6a at selected faces of the core. Therefore, by arranging the coupling means 61, 62, 63 in optical contact with the cladding 6a, it is possible to couple the light from the fiber out by capturing the evanescent field extending to the outside of the cladding. it can.
Correspondingly, light can also be coupled into the fiber by an evanescent field extending from the coupling means into the fiber core. By using separate evanescent coupling means 61, 62, 63 arranged on each resonant part,
Light can be wavelength-separated into / from the fiber core, and each coupling means 61, 62, 63
Only predetermined wavelength components are combined. For example, the wavelength component 11 is coupled to / from the waveguide at the resonant portion 21 by the coupling means 61, and so on.

In a preferred variant of the embodiment, the evanescent coupling means 61, 62,
63 includes a Fabry-Perot type fiber etalon. Thereby, optical coupling is only obtained for wavelengths that exhibit resonance at both the etalon and the associated resonant part of the chirped grating. Thus, when coupling light to / from the optical waveguide, the present invention can be used to obtain extremely high wavelength selectivity.

A fourth embodiment of the invention is shown in FIG. According to this embodiment, the sub-waveguide structure 5a is used as an intermediary when coupling light to / from the optical waveguide 1 such as an optical fiber. Preferably, the sub-waveguide structure 5a comprises a diffraction grating 2a of the same type as the diffraction grating 2 arranged in the main waveguide 5. If these diffraction gratings are two chirped diffraction gratings, the coupling strength between the sub-waveguide structure 5a and the main waveguide 5 is significantly increased under certain specific phase conditions. Appropriate means 61, 62, 63 for output or input coupling of light are suitably arranged adjacent to said sub-waveguide structure (
Or operatively connected). Although shown as evanescent coupling means in the drawings, of course any suitable means may be provided, said embodiments comprising:
This is an example. As described above, the important advantage of coupling the light to / from the waveguide 1 using the sub-waveguide structure 5a is that the coupling with the light propagating in the main waveguide is important except for the wavelength components to be coupled. It means that it does not have a great influence. The evanescent coupling can be weak enough to ensure that coupling of unintended wavelength components is essentially negligible. Another advantage of this embodiment is that the requirement for deep index modulation of the phase grating is less stringent, which in some cases is advantageous from a manufacturing standpoint. Furthermore, it may be advantageous to provide said diffraction gratings (chirp diffraction gratings) which have different modulation depths but are otherwise the same. In this way, the optical coupling operation can be customized even more precisely for a given application.

A preferred embodiment according to the present invention for incoupling light into an optical waveguide is shown in FIG. Again, the means for producing the local wavelength-specific resonant portion is represented by the chirp phase grating 2. In said figure, said means for coupling light into and out of the optical waveguide is represented by a tilted diffraction grating 3. The figure shows three separate light sources (eg lasers) 71, 72, 73 emitting three different wavelength components 11, 12, 13 of light. The emitted light is coupled into the waveguide 1 at the resonant portions 21, 22, 23 corresponding to each wavelength component. Certain types of collection optics 81, 82, 83 are suitably used for this incoupling. It is particularly preferred that each resonant portion 21, 22, 23 of the waveguide fulfills one function of a cavity mirror in the laser. In that case, the light sources 71, 72, 73 comprise one of a light-generating medium and one of the mirrors of the laser cavity, and use feedback, and thus the resonance of the laser operation in the waveguide, which acts as the feedback cavity mirror of the laser. Provided. The main advantage of this embodiment is that the laser emission wavelength is
This means that the corresponding part of the waveguide is fixed at the resonant wavelength (because sufficient feedback occurs only at this wavelength). Of course, it is also possible to use a separate external laser, the emission wavelength of the laser being coupled into the waveguide at the part that resonates at this wavelength.

An alternative way of achieving outcoupling of light is to bend the waveguide, which results in a controlled leakage of light out of the waveguide structure. Then, the waveguide component coupled from the waveguide at a predetermined position along the waveguide can be controlled by changing the bending. The optical fiber may, for example, be wrapped around a cylinder, the control being achieved by expanding or contracting the cylinder. From the technical point of view, it is somewhat difficult, but in principle, it is also possible to couple the light in by bending the optical fiber.

It should be noted that the wavelength components mentioned above are not essential, but they may themselves comprise several distinct wavelengths. For example, it is conceivable to use optical coupling in which a signal in one incident optical fiber is divided into three outgoing optical fibers, and the signal coupled to the first outgoing fiber forms a portion of the first wavelength component. .

[Brief description of drawings]

[Figure 1]   Figure 4 shows output coupling from an optical fiber using a tilted phase grating according to the prior art.

FIG. 2 shows outcoupling from an optical fiber using a chirped tilted phase grating according to the prior art to obtain the focal line of the outcoupled light.

FIG. 3 shows output coupling from an optical fiber using a chirped tilted phase grating in which prisms are used to allow a low tilt angle according to the prior art.

FIG. 4 is a schematic diagram showing how a resonance portion is generated for three arbitrarily selected wavelength components in different portions of an optical waveguide using a chirped Bragg grating.

FIG. 5 is a schematic diagram showing wavelength-selective outcoupling of light from a waveguide according to the first preferred embodiment of the present invention.

FIG. 6 is a schematic diagram showing wavelength-selective outcoupling of light from a waveguide according to a second preferred embodiment of the present invention.

FIG. 7 is a schematic diagram showing wavelength-selective outcoupling of light from a waveguide according to a third preferred embodiment of the present invention.

FIG. 8 is a schematic diagram showing wavelength-selective outcoupling of light from a waveguide according to a preferred embodiment in which a sub-waveguide is utilized as an intermediary for outcoupling.

FIG. 9 is a schematic diagram showing the incoupling of light into a waveguide according to the invention in which the diffraction grating structure of the waveguide forms part of a light generating means (eg a laser).

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, K E, LS, MW, MZ, SD, SL, SZ, TZ, UG , ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, BZ, C A, CH, CN, CR, CU, CZ, DE, DK, DM , DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, K E, KG, KP, KR, KZ, LC, LK, LR, LS , LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, MZ, NO, NZ, PL, PT, RO, R U, SD, SE, SG, SI, SK, SL, TJ, TM , TR, TT, TZ, UA, UG, US, UZ, VN, YU, ZA, ZW (72) Inventor Raoul Stube             Sweden S-182 75 Stocks             Hand. Cornwegen 21 F-term (reference) 2H037 BA00 CA33                 2H047 KA03 KB06 LA03 MA01                 2H049 AA06 AA41 AA62 AA66

Claims (24)

[Claims] 1. A method for coupling light into or out of an optical waveguide (1), said method being intended to couple specific wavelength components (11, 12, 13) of the light. In the portion of the waveguide, local resonance (21, 22, 23) for the wavelength component is generated.
), And coupling the wavelength component to or from the optical waveguide at the locally resonant portion. 2. The method according to claim 1, wherein a plurality of spatially separated portions having local resonances for different wavelength components are established in the optical waveguide. 3. A local resonance for a particular wavelength component selected from a plurality of wavelength components forming a part of the light is established in the part intended to couple said particular wavelength component. The method according to claim 1 or claim 2. 4. The method according to claim 1, wherein a local resonance is established for a continuum of wavelength components distributed in the wavelength-specific part along the waveguide. 5. The local resonance is caused by a chirp diffraction grating (2) in the waveguide.
The method of claim 4, wherein the method is established by providing. 6. Coupling of light to and from the optical waveguide is performed by a phase diffraction grating (3) having a diffraction grating element whose plane intersects the propagation axis of the waveguide structure at an angle other than 90 degrees. The method according to any one of claims 1 to 5, which is performed. 7. The method according to claim 1, wherein the coupling of light into or out of the optical waveguide is performed by a laterally asymmetric phase grating (4). 8. The method according to claim 1, wherein the coupling of light into or out of the optical waveguide is performed using bending of the optical waveguide. 9. The method according to claim 1, wherein the coupling of light to or from the optical waveguide is performed by evanescent optical coupling. 10. The coupling of light to and from the optical waveguide is a fabric
This is done by arranging a Pero-type fiber etalon adjacent to the optical waveguide, which enables optical coupling to or from the optical waveguide of only the wavelength component that satisfies the resonance condition of the fiber etalon. The method according to claim 9, which comprises: 11. A method according to any one of the preceding claims, wherein a sub-waveguide structure (5a) is used as an intermediary in coupling light into or out of the optical waveguide. 12. The method of claim 11, wherein the coupling between the sub-waveguide structure and the optical waveguide is an evanescent coupling. 13. At least one optical waveguide (1) having a waveguide structure adapted to guide light along a predetermined propagation axis, and means for coupling light to or from the optical waveguide. An optical coupling device comprising: a portion of an optical waveguide associated with resonance for a specific wavelength component, the specific wavelength component (11
, 12, 13) for providing local resonances (21, 22, 23) to the optical waveguide, the means for coupling light into or out of the optical waveguide being at the resonant portion associated with the wavelength component. Or an optical coupling device comprising being adapted to couple said wavelength components from an optical waveguide. 14. Device according to claim 13, wherein the means for providing local resonance in the part comprises a phase grating (2) arranged in a waveguide structure. 15. The apparatus according to claim 14, wherein the phase diffraction grating is a chirped diffraction grating, and a wavelength-specific portion along the chirped diffraction grating causes resonance to a continuum of wavelength components. 16. A means for coupling light into or out of an optical waveguide comprises a phase diffraction grating (3) having a diffraction grating element whose plane intersects the propagation axis of the waveguide structure at an angle other than 90 degrees. Device according to any one of claims 13 to 15. 17. Device according to any one of claims 13 to 15, wherein the means for coupling light into or out of the light guide comprises a laterally asymmetric phase grating (4). 18. Means for coupling light into or out of the optical waveguide is means for evanescent coupling of light into or out of the optical waveguide.
Device according to any one of claims 13 to 15 comprising 3). 19. A device according to claim 13, wherein the means for coupling light into or out of the light guide comprises bending of the light guide. 20. A Fabry-Perot type fiber wherein the means for coupling light into or out of the optical waveguide is disposed adjacent to the optical waveguide and provides evanescent optical coupling between the fiber etalon and the optical waveguide. 19. The apparatus of claim 18, comprising an etalon, thereby enabling optical coupling of only wavelength components that satisfy the resonance conditions of the fiber etalon to or from the optical waveguide. 21. A sub-waveguide structure (5a) for coupling light, the sub-waveguide structure forming an intermediary means for coupling light into or out of the waveguide. The device according to any one of 13 to 20. 22. The device according to claim 21, wherein the sub-waveguide structure (5a) and the main optical waveguide (1) both comprise a chirped diffraction grating (2, 2a). 23. The device according to claim 13, wherein the optical waveguide is an optical fiber. 24. The optical fiber is a single mode fiber.
The device according to.