JPS62500053A - Wavelength division multiplexers and demultiplexers - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention is based on optical fibers. fiber communication systems, especially wavelength-splitting multimeters with novel thin-film waveguide lenses. Regarding multiplexers/demultiplexers.

In optical fiber communications systems, each fiber typically transmits waves of a specific wavelength.

Current multiplexing technology can transmit hundreds of thousands of signals at this wavelength through single mm time multiplexing. I'm letting them send it. However, when the upper limit is reached, single fibers are at great loss. It must be equipped to satisfy the amount of information communication. Instead of increasing the number of fibers In addition, additional wavelengths are used within one fiber. Wavelength division multiplexers and demultiplexers A multiplexer is a device that accomplishes this. Transmitted by different wavelengths at the transmission end The signal to be output is fed into one single fiber by a multiplexer. Reception I11 At the end, the signals are collected into groups, each separated by a demultiplexer into a single Belongs to wavelength.

Currently, the wavelengths commonly used for optical communication are 800 nanometers and 13oO nanometers. It is an area within Tor. A third possibility is in the 1500 nanometer region. Ru.

A typical commercial demultiplexer separates only two completely different wavelengths, one for each region. It is one. However, as in particular technological improvements in light sources and laser light sources, Using many different wavelengths to increase the signal-carrying capacity of each optical fiber will become possible. Multiplexers and demultiplexers can handle this number of wavelengths. is required to effectively handle such increases.

The accompanying technology is integrated optics. A growing number of devices include integrated light Optical waveguide lenses remain the most basic. optical waveguide Lenses perform a variety of important functions, including focusing and referencing, and Fourier transformation. Converting, creating images, filtering spatial frequencies, and guided light and an assembly of beams.

There are many important design criteria for optical waveguide lenses. of the first diffraction spot Focal plane position, focal spot size, angular field of view, along with intensity curves and heels , the sidelobe energy and the loss of raw material 1 due to processing must all be taken into account. No. Equally important, the manufacturing technology should be simple, inexpensive and This must be achieved through administrative technology.

Currently - Most wavelength division multiplexers and demultiplexers on the market are Always using thin-film filters. When the wavelength is 2 or more, don't say n filters are used, and n-1 filters are used in a structure connected in series. The use of thin-film filters is poor because they must be filtered. This way Such devices are expensive to manufacture and suffer from signal depreciation.

The grating device can be used as a replacement for a thin one-film filter. Chinese and German The use of gratings against wavelengths is of course well known in spectroscopy and is described below. Optical signal multiplexer and demultiplexer from Canadian Patent No. 1.089,932 It is also well known for Plexa. Other methods of wavelength alone (, end, prism However, this has not been implemented commercially.

All I’? The device requires a device to standardize the light beam in order to reach the grating. requires a device that then focuses the beam. Bookkeeping - film Optical waveguide lenses are used to enable this referencing and focusing. Can be used as a device.

Bookkeeping - Three types of film optical waveguide lenses are proposed and guided optical beams. explained for use. Thin one-film Luneberg lens, general geometry waveguide lenses, and mode indexing lenses such as Fresnel diffraction lenses are discussed. It will be done. Each of these uses local changes within the optical waveguide. Change wavefront curvature index gradient, spherical indentation, and use grids. This local change in the waveguide structure causes scattering and Introducing mode modification will help eliminate this problem.

A type of multiplexer/demultiplexer that uses thin film lenses. Canadian patent granted to Northern Telecom on November 18, 1980 No. 1゜089.932, each of which includes optical miscellaneous, diffraction, ・Standard the light from an array of reflection gratings, focusing lenses, photodetectors, and light sources Use a lens that is calibrated to

In three-dimensional optics, the classification [refractive] index or [Grin Jt Kotto lens is It is in demand for many applications. There is a difference between the different Grinrod lens refractive index distributions. n−nosech<g), where nO is the effective refractive index at the beam tube axis. , Q is a constant (equal to π/2f, here is the radial distance, and all Meridian It is generally known that the onal rays can be focused.

It is an object of the present invention to overcome some of the problems and to overcome the wavelength division problems in the prior art. Multiplexers and demultiplexers offer advantages over wavelength f )〃Thin one-film wavelength laser for use in one multiplexer/demultiplexer The objective is to provide

Thus, according to aspects of the invention, the waveguide has a longitudinal axis and at each end of the waveguide. A multi-layer film that leaks the film waveguide that is essential to the line and the terminal surface is We offer thin-film, ilm waveguide lenses for use in plexers/demultiplexers. provide The plano-convex overlay, which is integral with the waveguide, extends the length of the waveguide along the axis; One end plane for substantially referenced or focused reach at the other terminal surface Normalizes the focused rays entering and focuses the focused rays The contours of the overlay layers are selected to yield a graded effective refractive index of the lens. It will be done.

According to another aspect of the invention, one of the terminal surfaces is adapted to receive an optical fiber in close relationship. said thin film forming an inlet/outlet plane iR and the other terminal surface supporting a diffraction/reflection grating. A multiplexer/demultiplexer with a film waveguide lens is provided. Ru. A focused ray entering the lens at the entrance/exit plane reaches the diffraction/reflection grating. The rays reflected from the diffraction/reflection grating are substantially normalized for the input/output As soon as it returns to the mouth plane, it is virtually focused and due to the close proximity of the optical 4HIIf The position is aligned with the spot position of the ray that is focused along the entrance/exit plane. It will be done.

is the effective refractive index at the waveguide axis, no is the effective refractive index at the waveguide axis, and Q are constants (equal to π/2f, where f is the focal length) and By notation, the shape of the plano-convex layer provides the effective refractive index profile of the waveguide. It seems so.

Further features of the invention may be set forth in or apparent from the following detailed description. Dew.

In order that the invention may be more clearly understood, the preferred embodiments will now be described with reference to the accompanying drawings and examples. (described in detail as shown)! ! will be done. In the attached diagram, Figure 7 shows the typical shape of a multiplexer/demultiplexer for two wavelengths. FIG. 3 is a plan view of a preferred embodiment of the comb.

Figure 2 shows the entrance plane A-A' of the multiplexer/demultiplexer lens. be.

FIG. 3 is a sectional view of the terminal surface B-8' of the lens.

Referring to the drawings, a preferred embodiment multiplexer/demultiplexer 1 is shown. has been done. For convenience, the device will be treated as a demultiplexer in this description. , it seems clear that the device can act in either role, simply acting in the direction of the signal. It just depends.

The input fiber Gfi F1 is connected to the input/output plane at −A′ to different wavelengths within the device. Therefore, the transmitted ig@ is supplied. The fibers IF2 and F3 have a representative output a[G fl, each transmitting a demultiplexed or wavelength-divided signal of a different wavelength. . In reality, of course, there are more than two wavelengths, and thus two typical output fibers F It will be more than 2 and 3. Due to the flow restriction of the light source, the output of about 10 or more power fibers at present, but specifically improved as a laser source and capable of different transmission wavelengths. It is unlikely to have a correspondingly large number of output fibers.

The device consists of a uniform thin-film waveguide 3 and an upper surface with carefully chosen relief contours. The rack consists of a uniform planar substrate 2 having a layer 4 . Overlay layer 4 is made of the same material FI (3 layers In the case of (in case of 4 layers). Optical INF1, F2 and F3 are the inlet/outlet of the device It is butt-bonded to a uniform thin one-film waveguide section 3 in the plane A-A'.

In the case of layer 4, a thin overlay of material similar to the film waveguide section 3 is then used. Instead of looking at the layer and the waveguide 3 as in Germany, the upper layer looks like they are exactly the same. It has been properly taken into consideration. However, for convenience of description, this specification Throughout, these will be referred to as separate elements. whether it is real or conceptual However, the wavy lines in Figures 2 and 3 indicate the dividing plane between these elements. It is used.

Integral diffraction/reflection grating at terminal face B-8' far from entrance/exit plane A-A' I have 5 children. The grid 5 is fitted or stamped onto the terminal surface B-8'. or otherwise provided, and suitable thin films provide high efficiency and low losses. It is placed on the grating 5 so as to turn into a reflective grating that has.

The graded effective refraction of the lens is used to standardize the rays reaching the diffraction/reflection grating 5. and the output fiber mF2. Entrance/exit according to the position of F3 etc. Let the wavelength-split rays leave the grating at a spot along the mouth plane A-A'. For focusing, the longitudinal direction INl of the thin-film waveguide 3 of the overlay Wi4 Aligned along the line, the overhang produces a plano-convex shape for layer 4, and the inlet/outlet It extends backwards in various ways from the plane A-A' to the terminal plane B-B' with the grid 5. Ru. Since the grating 5 is of course slightly angled from the longitudinal axis, the diffracted/reflected Is the signal in the input range? Slightly away from iF1, representative output y4 miscellaneous F2 and F3 directed towards.

It is known that the Linrod lens accurately focuses all meridional rays. It is. In a preferred embodiment of the invention, this index distribution is a Greenrod lens. With the plane of the thin one-film waveguide 3 coinciding with the meridional plane of applied to the two dimensions of the film waveguide 3, so that all incidences parallel to its axis It becomes a thin-film lens that focuses the light rays. - All-purpose suitable contour developed and this special contour is perfectly suitable as a contour for the layer 4 of the present invention. This has been determined by the present inventors.

The position of each output II is of course dependent on one wavelength captured by that one layer M. between fibers The difficulty in this is due to the separation of the wavelength 18I. e.g. at least one between the centers lIf [some physical separation, such as diameter, is preferred when signal focusing is inaccurate. It is desirable to avoid unwanted crosstalk, and to some extent it is unavoidable. ideal Each spot is essentially entirely focused within the circumference of the corresponding fiber M connection point. Therefore, there is essentially no lesson learned, and the focus adjustment characteristics of the present invention are such that this is essentially achieved. It seems that this should be done.

Optimal focal plane approximation of the rays to have a flat surface for different focal points of various wavelengths - Based on calculations from tracking data, it can be seen as an exaggeration from Figure 1. For the signal focus FJ4 node, a single-film waveguide with a thin entrance/exit plane A-A' is used. at a slight angle from a plane perpendicular to the axis of 3. Therefore the end with grid 5 Both minor face B-8' and entrance/exit plane A-A' are preferably slightly angled. . The order of the optimum optical focal plane 2 naturally depends on the angle chosen for the diffraction grating 5.

Diffraction-limited focusing is achieved by ray-tracing through the refractive index profile. It has been shown to be achievable for many focusing and reference requirements. Ray of light From the trace data, the size and location of the focal spot is determined.

This allows appropriate selection of output fiber diameter and focal plane position.

Creating the refractive index profile given by the above equation for a planar waveguide is an effective index. concepts are used. The bulk refractive index of the wavelength is constant, but the discrepancy - the film thickness The change changes the speed of the guided light wave. The result is that the propagation phase front is an appropriate effective finger. It is to have a speed equal to the bulk Buddhist painting in the material with the markings. suitable bulk The conductor is made of material and has a suitably shaped profile or a suitably overlay made of layer 4. In the wave tube the necessary effective distribution is obtained. This method works with single mode waveguides. most effective.

However, telecommunications currently use single mode fibers and are This is not an important limitation, since the optics are most suitable for single-mode techniques. .

A multilayer film to determine whether there is an actual material for the realization of this lens. The dispersion curves for film propagation were tested. For both cases of 3-layer and 4-layer The minimum and maximum values corresponding to the interruption of TEo and TE1 modes, respectively, are There is a waveguide thickness. Within this thickness range is an acceptable and effective refractive index distribution. gala 3-1 with a base board! Different focal lengths are constructed with the best waveguide material for the case of It turns out that it can be done. The only limitation is that the bulk waveguide refractive index is the refractive index of substrate 2. This creates a short focal length when approaching. Similarly, the flexibility configuration is 4-1!1 found for cases of and with different substrate materials.

The exact waveguide contour required to obtain the required effective rate distribution is the equation for the eigenvalues. obtained in tabular form by solving the required local efficiency, focusing Because of the local thickness, which gives the wavelength at which the beam is emitted, and the bulk refractive index of the material used, yields a dispersion curve. Such stages are considered routine work; It is also within the ordinary knowledge of those knowledgeable in this field.

This design is close together, with only one lens element and a monolithic grating. It is possible to separate all wavelengths into The unitary structure of the device is particularly effective and Since there are no discontinuities in the path, the same element can be used for both reference and focus adjustment. I can stay. Effective refraction extending from the entrance/exit plane A-A' to the diffraction/reflection grating 5 By the rate gradient, seellll! And no lens structure to get the focusing effect Uses a single-film waveguide. The above Canadian Patent No. 1,089,932 In contrast to existing devices such as The two dielectrically conductive boundaries between the lens and the planar waveguide are removed. Such an advance The technical device is used in areas of varying insulated thickness. This is done using a planar waveguide. The lens elements are placed adjacent to each other. Removing these boundaries is It has the potential to minimize de-transformation and scattering losses.

The device can be used as a multiplexer or as a demultiplexer with equal equipment It is easy to see from the above description that it can be operated in either direction, and that it simply depends on the direction of the signal. It will be recognized. When operated as a multiplexer, fiber F2. F3. etc The signals from are combined in the diffraction/reflection grating 5 and focused at Produces a synchronized output signal.

The lens is manufactured using existing technology used for Luneberg lens construction. from low-loss optical glasses to active materials such as lithium niobium oxide. Use a wide variety of materials.

Two methods could potentially be used to make such lenses. , No. 1, sputtering or evaporation is used with a suitable mask. Instead, a suitable A lens with a contour is molded into a deformed gel film that is immersed onto a substrate. Ru. A heat treatment then deforms the shaped gel within the inorganic hard oxide material. this Each Pi technique requires a combi coater assisted design and a highly accurate mask or mold. do. However, once a mask or mold is made, many lenses can be made. It can be used in many ways.

Keeping the manufacturing process within tolerances is very important and any errors in waveguide thickness should be avoided. The difference also increases aberrations, resulting in a corresponding error in lens focal length. however , the optimal focal plane is achieved through grinding and polishing of the waveguide edges, so the focal plane Small deviations in surface position are allowed.

The main complex techniques are explained by a simple description of their application in the manufacture of different parts of the equipment. Described below.

1. Fiber cutting - the end of each fiber must be created in a flat plane perpendicular to the 1g14% line. Must be.

2. Both ends of the thin film lens with a gloss coating (surface △ in Figures 2 and 3) A' and BB') and the fiber ends must also be polished.

3. Butt and stick together - use an appropriate resin as much as possible using an appropriate method. By dissolving the fibers against the end of the integral a-film waveguide 3, the conductor Accurate butt must be applied.

4. Bookkeeping - Film +7! Attachment - A suitable J-zoza film is welded to the flat surface of the base. must be In addition, the end surface BB' (Fig. 3) is Must have the appropriate film used, dipping and baking techniques Proposed.

5 type additional knee This technique is performed by predetermining the top of the monolithic thin-film waveguide 3. Molding is used to form contours and curved surfaces. Also to manufacture grid 5 used.

6. Conventional bookkeeping - film welding - thick film has very high efficiency and very low pores must be welded to the grating 5 so as to turn it into a reflective grating with one loss. vinegar For patter, a high-air evaporator is used.

This new optical waveguide lens has been analyzed and its manufacturing and focusing characteristics Theoretically tested. theorical! Existing shadow mass with I construction tolerance It was found that this method is compatible with the spattering technology and the new molding processing technology. flexible Certain critical Q stages allow its manufacture using a variety of materials. word mouth tracing rays This indicates that limited focus adjustment should be possible. Also, a low f-number The promise of ``designed for the use of integrated optical circuits that has been obtained and miniaturized'' is made. mold The processing technique is probably suitable for large M production, and compared with the existing methods of The price will be lower than when

In Figures 2 and 3, the connection between the thin Fillem waveguide 3 and the overlay FfJ4 is shown. The force is shown such that the layer overlying the dividing plane I between has zero thickness at the edge of the waveguide. , the plane is positioned so that the overlay layer has a limited thickness at the waveguide edge. is noteworthy. 3 In the case of one layer (, if N1 is imaginary rather than real) Therefore, this (of course, it is only relevant in the 4th layer).

It will be appreciated that the above description refers to preferred embodiments by way of example only. Book Many modifications to the invention will be obvious to those knowledgeable in this field, and Obvious changes to the This is within the scope of the present invention.

A day International Commission 8 Report 1, I@fflj116ml A#l1llj11゜,, a, PCT/GB 85100362-2-ANNEX To THE INTERNATION AL　5EARCHREPORT　ON

Claims (12)

[Claims] 1. Thin-film waveguide lenses for use in multiplexers/demultiplexers a thin-film waveguide having a longitudinal axis; at the joint end of said waveguide; an end plane essentially perpendicular to the waveguide; a plano-convex overlay integral with the waveguide; and extending the length of the waveguide along the axis, a focused beam of light and substantially collimated or focused at the other end plane. to focus a collimated ray entering one of the end planes for arrival. The contour of the overlay layer is selected to yield an effective refractive index for the lens class. A thin film conductor for use in multiplexers/demultiplexers characterized by Wave tube lens. 2. In the lens according to claim 1, the plano-convex overlayer has a shape according to the formula n= nosech(gr), where n is the effective refractive index at a distance r from the axis , no is the effective refractive index on the axis, and g is a constant equal to π/2f. where f is the focal length of the lens and the distance between the end planes is Having such an effective wind refractive index profile of the waveguide by Eq. lens. 3. The lens according to claim 1, wherein the material of the overlay layer is A lens characterized in that it is made of the same material. 4. The lens according to claim 2, wherein the material of the overlay layer is A lens characterized in that it is made of the same material. 5. For multiplexer/demultiplexer with thin single-film waveguide lens wherein the lens comprises a thin one-film waveguide having a longitudinal axis; an end plane essentially perpendicular to said axis at each end of the tube; integral with said waveguide; a plano-convex overlay extending the length of the waveguide along the axis; one said end for substantially collimated or focused reaching in an end plane; collimating a focused ray entering a plane and focusing a collimated ray The contour of the overlay layer is in front so as to yield a graded effective refractive index of the lens. selected for lens length; entered to receive optical fiber in adjacent relationship; one said end plane forming the mouth/exit plane; the other front plane supporting the diffraction/reflection grating; a focal point entering the lens at the entrance/exit plane; The combined light beam is substantially collimated to reach said diffraction/reflection grating; rays reflected from said diffraction/reflection grating back to said entrance/exit plane. When the optical fiber is substantially focused, the position for the adjacent optical fiber is determined by the entry. Be able to align the spot position of the focused ray along the mouth/exit plane A multiplexer/demultiplexer featuring: 6. In the multiplexer/demultiplexer according to claim 5, the formula n=nosech(gr), where n is the effective deflection toward the distance r from said axis. index of refraction, no is the effective index of refraction at said axis, and g is a constant equal to π/2f , where f is the focal length of the lens and the entrance/exit plane and the diffraction/reflection The effective refractive index block of the waveguide is determined by the above equation. The multiplayer layer is characterized in that the shape of the plano-convex top layer is such that the plano-convex overlayer has a shape that Tsukusu/Demultiplex Tsukusa. 7. The multiplexer/demultiplexer according to claim 5, wherein the A multiplexer characterized in that the material of the overlay layer is the same as the material of the waveguide. Support/Demultiplexer. 8. The multiplexer/demultiplexer according to claim 6, wherein the A multiplexer characterized in that the material of the overlay layer is the same as the material of the waveguide. Support/Demultiplexer. 9. The multiplexer/demultiplexer according to claim 5, wherein the inlet /Flat one-plane analogy for focused spot position along the exit plane such that the end planes constituting the entrance/exit planes have an optimal focal plane of A multi-layer structure that allows a slight angle from a plane perpendicular to the waveguide axis. Plexer/Demultiplexer. 10. In the multiplexer/demultiplexer according to claim 6, the input A flat plane for the spot position of the focused ray along the mouth/exit plane. the edges constituting the entrance/exit planes so as to have plane-like optimal focal planes; characterized in that the plane is slightly angled from a plane perpendicular to the waveguide axis. multiplexer/demultiplexer. 11. In the multiplexer/demultiplexer according to claim 7, the input A flat plane for the spot position of the focused ray along the mouth/exit plane. the edges constituting the entrance/exit planes so as to have plane-like optimal focal planes; characterized in that the plane has a slight angle from a plane perpendicular to the waveguide axis. multiplexer/demultiplexer. 12. In the multiplexer/demultiplexer according to claim 8, the input A flat plane for the spot position of the focused ray along the mouth/exit plane. the edges constituting the entrance/exit planes so as to have plane-like optimal focal planes; characterized in that the plane is a plane perpendicular to the waveguide axis or has a slight angle with the axis of the waveguide. multiplexer/demultiplexer.