DE102006025410A1 - Demultiplexer for e.g. optical data transmission, has coupler provided for coupling with input waveguides, where coupler is attached to waveguide array and has section whose cross section reduces towards waveguide array - Google Patents

Abstract

The demultiplexer has an input coupler (2a) provided for coupling with input waveguides (5), where the coupler is attached to a waveguide array (3). The input coupler has a section (2b), whose cross section reduces towards the waveguide array. An output coupler (4a) is provided for coupling with two output waveguides (6). The output coupler is attached to the waveguide array. The section of the input coupler has a partially convex cross section.

Description

The The invention relates to a demultiplexer for the telecommunications sector and data transmission, in particular a demultiplexer for an optical data transmission.

in the Area of optical data transmission is common in today's fiber optic networks the so-called DWDM method (DWDM = Dense Wavelength Division Multiplexing) used. In this procedure, data is transmitted through several light signals at different center wavelengths in transmitted to the same fiber. Since these light signals do not influence each other, can be by increasing the number of signals the total transmission rate increase. For transmission the different light signals in the same fiber will be like that called multiplexer needed the light signals of different wavelengths in the same fiber couples. At the end of the glass fiber is a corresponding demultiplexer necessary to return the overall signal to the individual light signals divide.

For the realization of such demultiplexers, the use of so-called AWGs (English for "Arrayed Waveguide Gratings") offers. 7 shows a schematic representation of such an "Arrayed Waveguide Gratings". Essentially, this includes a waveguide array 3 (English: "Phase Array"), which has a plurality of individual waveguides, which are semicircular in the present example. The array 3 is with one or more input waveguides 5 and a plurality of output waveguides 6 coupled.

The coupling elements 2 and 4 are also referred to as "Free Propagation Region" or short as FPR elements. The task of the first coupler 2 (also called input coupler) is that of the first waveguide 5 Exiting total light signal on the individual waveguides of the array 3 through which the light then passes in the direction of the second coupler 4 (also called output coupler) propagates.

The length of the individual waveguides of the waveguide array 3 is chosen such that the length difference of the optical path (dL) of two adjacent waveguides of the array 3 corresponds to an integer multiple of a central wavelength for which the demultiplexer is provided. Under this condition, the field distributions of the individual light signals in the waveguide array 3 at the beginning of the second coupler 4 essentially an equal phase to each other. This turns the field distribution into the end or output area of the input coupler 2 is present, in the beginning or input area of the output coupler 4 reproduced. Due to the constant difference in length dL of adjacent waveguides in the waveguide array 3 the phase difference ΔΦ increases linearly from inside to outside. This diffracts the wavefront as a whole, resulting in a focal point in the image plane 7 moved away from the center of the image plane. By suitable positioning of the output waveguides 6 along the image plane at the end of the output coupler 4 can be selected which wavelength and thus which light signals are assigned to the respective output waveguides.

The needs to increasing transmission rates to lead in that within the useable transmission window specified in fiber optic networks the wavelength distances (called channel spacing from the English Channel Spacing ") between the individual to be transferred Light signals are reduced. In this way, the number of Light signals within the transmission window for the respective Fiberglass increased become.

The problem here may be that due to the reduction of the channel spacing between two adjacent light signals crosstalk (English "cross talk") between the individual channels increases greatly. The reason for this are phase and amplitude errors that increase with decreasing channel spacing. For example, a phase error may occur at the end of the waveguide array 3 due to technological errors, such as geometric variations of the waveguide, stress fields, variations in the doping, etc. arise. Since the difference in length dL between two adjacent waveguides increases with a reduced channel spacing, the entire length of the waveguides in the waveguide array also increases and as a result a phase error increases. In order to reduce this problem, it is important to make the length difference dL small, making it necessary to extend the input and output couplers. However, the amplitude errors and thus the noise in the field distribution in the end or output region of the input coupler increase. 6 shows the field distribution (E-Field) as a function of the width at the end of the input coupler with an "Arrayed Waveguide Gratings" with 200 channels and 25 GHz channel spacing, from which the noise is visible.

task The invention is to provide a demultiplexer in which the Amplitude error is reduced.

These Task becomes with the objects of the independent claims 1 and 15 solved. advantageous Embodiments and developments of the invention are the subject the dependent Claims.

The Cause for the amplitude error lies essentially in the noise of the field distribution established at the end of the first coupler. To reduce this noise, the invention provides form the geometric shape of the first coupler so that this has at least a first portion whose cross-section is in the direction of the waveguide array or in the propagation direction the light signal is reduced.

• 1. ein Wellenleiterarray;
• 2. einen ersten Koppler ausgebildet zum Koppeln mit einem oder mehreren Eingangswellenleitern, der erste Koppler an das Wellenleiterarray angeschlossen, wobei wenigstens der erste Koppler einen ersten Abschnitt aufweist, dessen Querschnitt sich in Richtung auf das Wellenleiterarray hin und/oder sich in einer Ausbreitungsrichtung des dem ersten Koppler zugeführten Lichts verringert.

A demultiplexer for data transmission according to the invention comprises:

• 1. a waveguide array;
• 2. a first coupler adapted for coupling to one or more input waveguides, the first coupler connected to the waveguide array, wherein at least the first coupler having a first portion whose cross-section towards the waveguide array towards and / or in a propagation direction of the first coupler light supplied reduced.

In an execution the waveguide further comprises a second coupler for coupling to at least two output waveguides connected to the Waveguide array is connected. In one embodiment of Invention, the second coupler also has a portion whose Cross-section is reduced towards the waveguide array. In other words, the portion of the second coupler is designed to that it increases in the propagation direction of the light. In a general Ausges tion contains the modified coupler a section with convex sidewalls.

Next the general shape with convex sidewalls may be the first section of the first or second coupler also have a different shape. For example, it may have an exponentially changing cross section, a hyperbolic, logarithmic or parabolic changing cross section. It is essential that the section of the first or second Coupler tapers towards the waveguide array.

The inventive modification the geometry of at least the first coupler in a demultiplexer is opposite Insensitive to technological fluctuations. In other words the Technology influences the positive impact of the modified Coupler on the crosstalk is not. In the invention, a reduction of the crosstalk of signal components in neighboring channels independently from the other characteristic parameters of the demultiplexer reached. Thus lets the "Crosstalk" is independent of an insertion loss (English: "insertion loss") or a nonuniformity (Non-Uniformity).

The Invention can be preferably used as a demultiplexer. at a substantially symmetrical structure, the arrangement but also a multiplexer and can be used as such. In this respect, the invention is both as a multiplexer and as a demultiplexer suitable.

in the Further, the invention with reference to several embodiments with reference explained in detail on the drawings. Show it:

1 A first embodiment of a free propagation region coupler with a modified geometry according to the invention,

2 a first schematic representation of a demultiplexer ("Arrayed Waveguide Gratings") with modified input and output couplers according to the invention,

3A A second embodiment of a coupler according to the invention,

3B A third embodiment of a coupler according to the invention,

3C A fourth embodiment of a coupler according to the invention,

3D A fifth embodiment of a coupler according to the invention,

4 a second schematic representation of an embodiment of a demultiplexer with coupler according to the invention,

5 a diagram of an exemplary field distribution of a light signal as a function of the width at the end of a coupler according to the invention,

6 a diagram of an exemplary field distribution of a signal as a function of the width in a conventional coupler,

7 a schematic representation of a known demultiplexer,

8A an embodiment of a known coupler,

8B A second embodiment of a known coupler.

8A shows a plan view of a known coupler 2 , as for example in the demultiplexer 7 is used. The term coupler means a region of the demultiplexer the one in which one via an input waveguide 5 can freely propagate coupled light. Such an area is called "Free Propagation Region" (FPR for short). It serves to evenly distribute the light signal emerging from the input waveguide, in order to enable the simplest possible and lossless coupling into a waveguide array.

In the present case, the coupler includes 2 a substantially rectangular geometry. The input waveguide 5 can over a Taper 51 be connected to a first side of the coupler. The taper 51 represents a cross-sectional widening of the waveguide 5 In the same way, even at the end of the FPR 2 several tapers 31 be provided, to each of which a waveguide 3a connected. Another known embodiment shows 8B in which the coupler 2 is designed as a free propagation region with a wedge-shaped geometry that opens to the waveguide array.

For reasons of symmetry is in the same way between the output of the waveguide array 3 and the plurality of output waveguides 6 a coupler 4 arranged. In the present case, the coupler includes 4 the same rectangular geometry as coupler 2 , In the same way both at the beginning of the FPR 4 several tapers 31 be provided, to each of which a waveguide 3a is connected as well as at the end of the FPR 4 several tapers 61 can be provided, to each of which an output waveguide 6 connected.

1 shows an embodiment of a coupler 2 with an altered geometry according to the invention. The coupler 2 includes a first section 2 B as well as a second section 2c which are arranged mirror-symmetrically with respect to a transverse axis X1. The respective axis sections have sidewalls 21b respectively. 21c , which in particular can be convex. In the signal input area 21 concludes the coupler with a slightly curved wall, to which the taper 51 and the input waveguide 5 connected. On the output side are several tapers 31 provided with a plurality of respective output waveguides 3a are connected. These are part of a waveguide array or phase arrays, not shown below 3 ,

The second section 2c In terms of its geometric arrangement corresponds in part to the known coupler 8B , The section 2d however, includes exterior walls 21b whose distance from each other towards the taper 31 and the waveguide array 3 is reduced. In other words, the cross section Q1 of the section becomes 2 B in the propagation direction of the light, here indicated by hν, lower. As shown here, the coupler has 2 in the axis X1, which corresponds to half its longitudinal extent, also its largest transverse extent. Thereafter, the cross section in the first section tapers 2 B again in the end area 22 on which the tapers 31 are attached.

By modifying the geometric arrangement, the amplitude noise is reduced and thus a crosstalk of different signal components is reduced. In addition, now through special taper 51 and 31 further optimizations are made at the input or output of the coupler. For example, tapered parabolas can be used, resulting in a much flatter pass band. As a result, an optimization with regard to crosstalk of different light signals can be achieved independently of other improvements.

2 shows an embodiment of a demultiplexer with an input coupler 2a and an output coupler 4a which each in 1 have shown geometric configuration. The coupler 2a is arranged so that the tapered section 2 B with its smallest diameter in the end area 22 to the waveguide array 3 connected. This achieves the reduction of noise in the amplitude distribution.

For reasons of symmetry is in the same way between the output of the waveguide array 3 and the plurality of output waveguides 6 a coupler 4a arranged. In the coupler 4a the light signal divided into the waveguide array is brought together again and into a point on the image plane at the end of the coupler 4a focused. The first section of the coupler 4b also tapers towards the waveguide array. With respect to the light propagation direction indicated by the dotted arrow, the cross section of the section increases 4b in the second coupler. Due to the illustrated symmetrical shape, the demultiplexer can also be used as a multiplexer with the same technical advantages when the light propagation direction is reversed.

5 shows the field distribution as a function of the width in the coupler according to the invention 1 in the same demultiplexer with 200 channels and 25 GHz channel spacing. It can be clearly seen that compared to the field distribution in a known coupler after 6 the amplitude noise is greatly reduced.

3A shows a further embodiment of the coupler according to the invention. This coupler includes a second rectangular section 2d , the two side walls substantially parallel spaced Q3 21d having. The entrance area 21 is also here by a curved öff formed at the end of the wall. From the dashed line X3, the cross section Q2 becomes toward the end region 22 lower. Unlike the in 2 shown linear decrease of the cross section in the section 2 B in the present case, the acceptance takes place in the section 2 B in the coupler according to the embodiment of the 3A not linear but slightly exponential.

The in 3B shown coupler is wedge-shaped and has only the tapering in its cross section section 2 B on. In other words, in this embodiment has the input area 21 the largest cross-section that is continuous to the exit area 22 away and thus reduced in the propagation direction of the light.

In addition to this simple wedge shape with the taper towards the waveguide array, shows 3C an embodiment of a "Free Propagation Region" with a section 2c in which the distance between the opposite side walls 21c increases. Connected to this is a second section 2 B in which is the distance between the side walls 21b again reduced. In contrast to the embodiment of 2 are however the sections 2 B and 2c not mirror-symmetric with respect to the axis X1.

3D shows a similar coupler, wherein the input area and output area are reversed. Depending on the length of the coupler according to the 3C and 3D the increase of the cross section occurs in the section 2C as well as the decrease in the section 2 B differently. In the illustrated embodiments in 3C and 3D the width of the input or output area is the same size. It is possible to choose the width of the areas of different sizes.

4 shows a further embodiment of a demultiplexer according to the invention with an input coupler with altered geometry. The input coupler 2 is about one or more tapers 51 in its entrance to the input waveguides 5 connected. The coupler essentially corresponds to the coupler according to FIG 3A , So has a rectangular section with constant cross-section, from the axis X1 in the section 2 B parabolic decreases. In the exit area 22 is the coupler 2 over several tapers 31 to the waveguide array 3 connected. The output coupler 4 is rectangular in this case.

The Embodiments and examples shown here can be in arbitrarily combine with each other. In addition to the regarding the Length of the respective couplers are linear decrease of the distance between the sidewalls Other geometric shapes of the side walls possible. For example, you can the side walls towards the waveguide array parabolic, hyperbolic, parabolic, taper logarithmically or exponentially. Also combinations of these Shapes are possible. The decrease may be different with respect to the length of the coupler done quickly. Also is a sectional enlargement of the cross section conceivable, followed by a reduction. An essential Aspect is that the area of the coupler that connects to the waveguide array connected or facing this, towards the Rejuvenated array.

2

Coupler, "Free Propagation Region"

2a

Coupler, "Free Propagation Region"

2 B, 2c

sections

21

entrance area

22

output range

21b, 21c

side walls

21d

side walls

3

Waveguide array

3a

waveguides

31 51

Taper

4

Coupler, "Free Propagation Region"

4a

Coupler, "Free Propagation Region"

4b, 4c

sections

5

Input waveguide

6

Output waveguides

X1, X2, X3

axes

hv

Light propagation direction

Q1, Q2, Q5

cross-section

Claims (17)

Demultiplexer for data transmission, in particular for optical data transmission, comprising: - a waveguide array ( 3 ); A first coupler ( 2 . 2a ) adapted for coupling to an input waveguide ( 5 ), the first coupler ( 2 . 2a ) to the waveguide array ( 3 ), the first coupler ( 2 . 2a ) a first section ( 2 B ) whose cross-section (Q1, Q2) towards the waveguide array ( 3 ), - a second coupler ( 4 . 4a ) adapted for coupling with at least two output waveguides ( 6 ), the second coupler ( 4 . 4a ) to the waveguide array ( 3 ) connected. A demultiplexer according to claim 1, further comprising: - one or more input waveguides ( 5 ) and at least two output waveguides ( 6 ). Demultiplexer according to one of Claims 1 to 2, in which the second coupler ( 4 . 4a ) a first section ( 4b ), whose cross-section is in Direction to the waveguide array ( 3 ) decreased. A demultiplexer according to any one of claims 1 to 3, wherein the first section ( 2 B . 4b ) at least partially has a convexly changing cross-section. A demultiplexer according to any one of claims 1 to 4, wherein the first section ( 2 B . 4b ) at least partially has an exponentially changing cross-section. Demultiplexer according to one of Claims 1 to 5, in which the first section ( 2 B . 4b ) at least partially has a linear or hyperbolic or logarithmic or parabolic changing cross section. Demultiplexer according to one of Claims 1 to 6, in which the first coupler ( 2 . 2a ) a second section ( 2c ) whose cross section in the direction of the waveguide array ( 3 ) remains constant. Demultiplexer according to one of Claims 1 to 7, in which the first coupler ( 2 . 2a ) a second from the waveguide array ( 3 ) facing away from ( 2c ) whose cross-section is directed towards the waveguide array ( 3 ) enlarged. Demultiplexer according to one of Claims 1 to 8, in which the second coupler ( 4 . 4a ) a second section ( 4c ) whose cross-section towards the waveguide array ( 3 ) remains constant. Demultiplexer according to one of Claims 1 to 9, in which the second coupler ( 4 . 4a ) one from the waveguide array ( 3 ) facing away from the second section ( 4c ) whose cross-section is directed towards the waveguide array ( 3 ). A demultiplexer according to any one of claims 1 to 10, wherein the first section ( 2 B . 4b ) of the first and / or second coupler ( 2 . 2a . 4 . 4a ) in the region of its smallest cross section to the waveguide array ( 3 ) connected. A demultiplexer according to any one of claims 7 to 11, wherein the first section ( 2 B ) to the second section ( 2c ) are mirror-symmetrical with respect to an axis (X1). Demultiplexer according to one of Claims 1 to 11, in which the first coupler ( 2 . 2a ) via one or more tapers ( 51 . 31 ) with the input waveguide ( 5 ) and / or with the waveguide array ( 3 ) connected is. Demultiplexer according to one of Claims 3 to 13, in which the second coupler ( 4 . 4a ) via one taper ( 51 . 31 ) with the at least two output waveguides ( 6 ) and / or with the waveguide array ( 3 ) connected is. A demultiplexer for optical data transmission, comprising: - an input waveguide ( 5 ) for supplying light; A waveguide array ( 3 ); A first coupler ( 2 . 2a ) connected between the input waveguide ( 5 ) and the waveguide array ( 3 ), the first coupler ( 2 . 2a ) a section ( 2 B ) whose cross-section (Q1, Q2) decreases in a propagation direction of the light. A demultiplexer according to claim 15, further comprising: - a second coupler ( 4 . 4a ) located between an output of the waveguide array ( 3 ) and at least two output waveguides ( 6 ), wherein the second coupler ( 4 . 4a ) a section ( 4b ), whose cross-section increases in the propagation direction of the light. Demultiplexer according to one of Claims 1 to 16, in which the waveguide array ( 3 ) is formed to a runtime-induced channel separation.