DE19742070C2 - Device for polarization-independent separation and superimposition of light signals - Google Patents

Description

The invention relates to a device for polar separation and overlay of ver light having different frequency components signals with coupling waveguides, which in at least open a free jet area, with at least a waveguide phase grating that is a number of each shift in pairs by an optical length the long trained phase shifting waveguides has and on the input and output side in a free jet area opens, and with at least a polarization conversion element with which the Polarization ratios of the light signals to Achieve a polarization-independent trans mission characteristics are changeable.

Such a device is from the article "Polarization Mode Converter With Polyimide Half Waveplate in silica-based planar lightwave Circuits "by Y. Inoue, Y. Ohmori, M. Kawachi et al. in IEEE Photonics Technology Letters, Vol. 6, No. 5, May 1994, pages 626 to 628. At the known device are Koppelwellenlei ter provided, each in a free jet flow richly. Between the free jet areas is a polarization independent trans mission characteristic waveguide phase grating formed over a variety ver in pairs by an optical length long phase shift waveguide. In the previously known device, the phases sliding waveguide from one in the middle of the  Phase shifting waveguide running gap below breaks in which a relatively thin and thus low loss, as a λ / 2 delay element designed polyimide plate is inserted. By the resulting conversion of transver sal-magnetic and transverse-electric Light components are largely polarizing independent transmission characteristics achieved. However, the previously known device has the Disadvantage that the polyimide plate gap and the polyimide plate itself the entire length must be executed with high precision high optical quality, especially in the rear look at the spectral resolution of the To ensure waveguide phase grating.

From US-A-5,440,416 is a separating device and superimposing light signals with difference Lichen frequency components known that over two Free jet areas, between which one off a number of phases of different optical lengths phase shifting wave formed lenleitergitter is arranged. In the entrance The first free jet area leads to an entrance waveguide, which is used to apply optical Signals with a number of frequency components is provided. In the output second On the one hand, the free jet area opens out at the exit term ends of the phase shift waveguide and another a waveguide that connects one to several So-called broadcast Signal can be applied. In the output side connected to the second free jet area Coupling waveguides are each a frequency component of the in the first free jet  range of connected input waveguides led light signals as well as in that to the second free jet area connected waves wire-guided broadcast light signal can be fed.

The invention has for its object a Specify device of the type mentioned at the outset, those with high spectral resolution, ge lowest losses and low manufacturing costs a largely polarization-independent trans mission characteristics.

According to the invention, this object is achieved by that the or each polarization conversion element so arranged in the optical beam path of the respectively assigned free beam area net is that it with between the coupling waveguides and the phase shift waveguides running light sig nal shares is acted upon.

By arranging the or each polarization con version element in an assigned free jet on the one hand, the range remains for the spectral Resolving power of the device essential Phase shifting waveguide free of interruptions or manipulations after their manufacture, for another is a particularly small dimension of the or each polarization conversion element possible because the free jet areas compared to the relatively extensive waveguide phases grids are much smaller. Hence it follows with significantly reduced manufacturing costs high optical quality.

Two free jet areas are expedient provided in which the phase shift waveguide  mouth, with each free jet area a Polarisa tion conversion element is assigned.

In one embodiment, this is or each polar sationskonversionselement a polarization filter, with the transverse electrical components and transversal magnetic components of the Lichtsig nales spatially separable or superimposed are cash. In this embodiment, it is provided that that the waveguide phase grating is one for guiding the transversal magnetic component provided Partial waveguide phase grating and for guiding the Transversal electrical component provided Has partial waveguide phase grating, the attenuator for the guided transverse compos nents are the same. Through the overlay which also after passing through the waveguide phase grating relative to each other in their intensity unchanged transverse magnetic components and transverse electrical components of light signals is a polarization-independent trans Mission characteristics achieved.

Another embodiment provides the or each polarization conversion element as to form a λ / 4 delay element. In a further training in this regard is advisable the or each λ / 4 delay element reflective train and the assigned free jet area to be delimited. This allows a special ders compact construction with in the same direction oriented coupling waveguides and phase shifters achieve waveguides.  

To integrate the function of a star coupler it is appropriate that the device in one Distribution beam waveguide opening into free jet area has the same optical length, in which a so-called broadcast signal on with specific Coupling waveguides fed by frequency components is distributable. In another embodiment for this purpose a distribution waveguide seen that opens into a free jet area.

The or each polarization conversion element is For example, arranged in a recess at least one-sided to the assigned vacancy limits the beam area. The polarization conversion element in a hybrid design the exception filling completely into the recess glued or using the so-called sputter technique one against the assigned free jet area zenden wall of the recess may be applied.

Further expedient configurations and advantages the invention are the subject of the dependent claims and the following description of exec tion examples of the invention with reference to the Figures of the drawing. Show it:

A waveguide chip with a erfindungsge MAESSEN device, which is housed in a casing and components to the Peripheriekom are connected FIG. 1 in a perspective view;

Fig. 2 is a perspective view of an off an inventive device with two guide for each a reflective ausgestaltetes λ / 4 retardation element has facing free-jet areas constructed lenleiterchip as Wel,

Fig. 3 shows the arrangement according to Fig. 2 in top view,

Fig. 4 is a perspective view of an embodiment of the Wei terbildung according to Fig. 2 and Fig. 3,

Figure 5 shows the further embodiment according to Fig. 4 view. In plan,

Fig. 6 in a plan view a further exporting an approximately example on a waveguide chip realized according to the invention before direction / has 4 delay elements two reflective configured in the wavelength range transmissive and in another wavelength range λ, which are introduced into two free-jet areas,

Fig. 7 in a plan view an embodiment of an inventive device provided in two free-jet areas Pola risationsfiltern,

Fig. 8 in cross-section a part of a recess provided with a free-jet region in which a polarization conversion element is introduced and

Fig. 9 in cross-section a part of a recess provided with a free-jet region in which a polarization conversion element in sputtering technique is introduced.

Fig. 1 shows a perspective view of a waveguide chip 1, which is built with a device according to the Invention for polarization-independent separation and superimposition of different Fre frequency components having light signals. The waveguide chip 1 is applied to a chip carrier 2 which is connected to a thermoelectric cooling unit which can be controlled via a cooling connection socket 3. The waveguide chip 1 is optically coupled to fiber bundle couplers 4 and to a fiber coupler 5 , which are connected to fiber bundles 7 running in fiber spouts 6 at the ends. About the fiber bundle 7 , the waveguide chip 1 light signals, preferably in the infrared spectral range with several different frequency components in the range of 1.3 microns and 1.5 microns can be coupled or from the waveguide chip 1 from. Furthermore, a housing 8 is provided which takes the waveguide chip 1 , the fiber bundle coupler 4 , the fiber coupler 5 and the cooling unit and to which the fiber connection socket 3 and the fiber grommets 6 are attached.

Fig. 2 shows a perspective view of a waveguide chip 1 , in which an embodiment example of an inventive device is inte grated. The waveguide chip 1 has a substrate 9 , on which a waveguide carrier layer 10 is applied. In the waveguide carrier layer 10 , a number of coupling waveguides 11 of a first coupling waveguide group 12 are introduced, which end on the one hand on a first coupling side 13 of the waveguide chip 1 and on the other end in a first free radiation area 14 . The first free beam region 14 is formed as a two-dimensionally relatively extensive waveguide layer with a rounded border, in which, for example, light radiation that is coupled in via the coupling waveguide 11 can freely spread in two dimensions.

The first free radiation region 14 is arranged on the edge side of the waveguide carrier layer 10 and, in the extension of the coupling waveguide 11, is completed with a first edge reflection filter 15 as a polarization conversion element. The first Randre flexionsfilter 15 is constructed from a plurality of di electrical layers of different optical thickness, which reflect incident light within a certain spectral range on the basis of multiple interferences and change its polarization composition, with incident linear polarized light reflecting circularly after reflection and incident zir Specularly polarized light is linearly polarized after reflection.

Furthermore, a number of phase shifting waveguides 16 of a waveguide phase grating 17 , which is constructed as a so-called "arrayed waveguide grating" (AWG), open into the first free beam region 14 . The phase shift waveguides 16 are formed in pairs to an optical length different lengths and open with their first free-jet region 14 in opposite ends of a second free-jet region 18, which is constructed in accordance with the first free-jet region 14 and disposed. The second free beam area 18 is corresponding to the first free beam area 14 by a second Randre reflection filter 19 completed as a polarization conversion element, which is constructed according to the first edge reflection filter 15 and is accordingly optically equivalent. The phase sliding waveguide 16 of the waveguide phase grating 17 extend on the same side as the coupling waveguide 11 of the first coupling waveguide group 12 between the free beam areas 14 , 18 in the direction of the edge reflection filter 15 , 19 opposite side of the waveguide carrier layer 10 and are example as in Fig. 2 shown arched or step-like formed with different arc length or step height and step width from.

The phase shifting waveguides 16 opposite open into the second free beam area 18 coupling waveguide 20 of a second coupling waveguide group 21 , the other ends of which end on one of the first coupling side 13 opposite second coupling side 22 of the waveguide carrier layer 10 and on the same side of the free radiation areas 14 , 18 as the phase shift waveguide 16 are arranged.

FIG. 3 shows a top view of the waveguide chip 1 according to FIG. 2. From FIG. 3 it can be seen that the free beam regions 14 , 18 , which are mirror-symmetrical to a longitudinal axis, are closed at the edges by the edge reflection filters 15 , 19 , the edge reflection filters 15 , 19 are constructed from a plurality of dielectric layers 23 extending over the edge side of the waveguide carrier layer 10 adjoining the free radiation regions 14 , 18 for manufacturing reasons.

In the apparatus of Fig. 2 and Fig. 3, the coupling waveguides 11, 20 of the Koppelwellenlei tergruppen 12, 21 and the phase shift shafts conductor 16 of the arrayed waveguide grating 17 so arranged that through input-side coupling waveguides 11, 20 of a coupling waveguide group 12, 21 coupled light signals with different frequency components after reflection at the edge reflection filter 15 , 19 first acted upon in the beam direction, enter the phase shifting waveguide 16 and after leaving the phase shifting waveguide 16 and reflection at the edge reflection filter 15 , 19 following in the beam direction due to the different optical length of the phase shifting waveguide 16 couple spectrally separated, each with a frequency component into the output coupling waveguide 11 , 20 of the other coupling waveguide group 12 , 21 .

At the input side of the device coupled linearly polarized light signals by correspondingly equipped orientation of the directions of incidence to the edge reflection filters 15, 19, the input polarization of the edge reflection filter 15, 19, incident light signals corresponding to the effect of a so-called λ / 4 Ver deceleration element in a circular polarization converted, which is applied back to linear polarization after the applied edge reflection filter 15 , 19 , which, however, is offset by 180 degrees with respect to the input polarization, is converted back. As a result, the waveguide phase grating 17 is interspersed with circularly polarized light, so that the transmission characteristic of the device as a whole is independent of polarization.

Fig. 4 shows a perspective view of a further development of the exemplary device according to Fig. 2 and Fig. 3, wherein in Fig. 2 to Fig. 4 corresponding elements are provided with the same reference characters and are not explained in more detail below. In the exemplary embodiment according to FIG. 4, the free beam areas 14 , 18 border an edge filter gap 24 , which is introduced into the waveguide carrier layer 10 and in which the edge reflection filters 15 , 19 of the free beam areas 14 , 18 are inserted in a hybrid construction. On the free beam areas 14 , 18 opposite side of the edge reflection filter 15 , 19 , a distribution waveguide 25 is introduced into the waveguide carrier layer 10 , which extends from the first coupling side 13 in the direction of the second randre flexion filter 19 and through this through into the second Open beam area 18 opens.

Fig. 5 shows a plan view of the waveguide chip 1 shown in FIG. 4. From Fig. 5 it can be seen that the edge reflection filter 15 , 19 extend only over the width of the free beam areas 14 , 18 , so that the edge reflection filter 15 , 19 relatively are inexpensive to manufacture.

In the further development according to FIG. 4 and FIG. 5 is provided in the distribution fiber 25 light signals having at least one Frequenzkomponen te as a so-called broadcast signal that is to be distributed to multiple recipients to couple the components in a different spectral region than the Frequenzkom of light signals coupled into the input-side coupling waves 11 of the first coupling waveguide groups 12 lie. The mouth area of the distribution waveguide 25 in the second free beam area 18 is angeord net that in the distribution waveguide 25 coupled light signals largely evenly couple in the coupling waveguide 20 of the second coupling wave conductor group 21, while the frequency components of in the coupling waveguide 11 of the first coupling waveguide group 12 fed light signals after passing through the Wellenlei terphasengitter 17 on individual coupling waveguide 20 of the second coupling waveguide group 21 are divided up. The embodiment according to FIGS. 4 and 5 characterized by the fact that in the term ausgangssei coupling waveguides 20 of the second Koppelwel lenleitergruppe 21 optical signals having different instantaneous frequency components are fed.

Fig. 6 shows a top view of another From guide for an inserted into a waveguide chip 1 an inventive device for polarization-independent cutting and superimposition of different frequency components having light signals being provided in the execution Fig. 2 embodiments according to Fig. 6, corresponding elements with the same reference numerals and are not explained in more detail below. In the off according to FIG operation example. 6, a first free is jet region 26 is provided in the coupling waveguide 11 of the first coupling waveguide group 12, the phase shift waveguide 16 of the wave conductor phase grating 17, coupling waveguide 27 of a third coupling waveguide group 28 and a number of optically equally long distributor shafts conductor 29 of a distribution waveguide group 30 open. The first free-jet region 26 shown in FIG. 6 has an oval-shaped or ellipsoidal rims and is interrupted along its transverse axis by a median filter gap 31, is inserted sion element in which a transmission filter 32 as Polarisationskonver.

In a second free-jet region 33 in addition to the phase shift waveguides 16 of optic phase grating 17, the coupling waveguides 20 lead the second coupling waveguide group 21 and the distri lerwellenleitern 29 of manifold waveguide group 30 coupling waveguide 34 of a fourth Koppelwel lenleitergruppe 35th The second free jet area 33 in the embodiment according to FIG. 6 is built up accordingly to the first free jet area 26 , a selective filter 36 being inserted as a polarization conversion element in the second free jet area 33 also coinciding with the transverse axis separating central filter gap 31 .

The embodiment of Fig. 6 is designed so that the coupling waveguides 11, 20 of the first coupling waveguide group 12 and the second coupling waveguide group 21 and the phase shift bewellenleiter 16 of the arrayed waveguide grating 17 on one side of the middle filtration gap 31 and the coupling waveguides 27, 34 of the third coupling shafts conductor group 28 and the fourth coupling waveguide group 35 and the distribution waveguide 29 of the distribution waveguide group 30 are arranged on the other side of the central filter gap 31 .

In the embodiment according to FIG. 6, the transmission filter 32 is so designed that in the coupling waveguides 11, 27 of the first coupling shafts conductor group 12 and the third coupling waveguide group 28 are coupled linearly polarized light signals having different frequency components in different spectral ranges, for example, at 1.3 micrometers and 1.5 microns, with conversion of the linear polarization into a circular polarization, so that light signals coupled into the first coupling waveguide group 12 are coupled into the distribution waveguide group 30 and into the third coupling waveguide group 28 a fed light signals into the waveguide phase grating 17 .

The selective filter 36 is designed such that it is highly reflective, for example, in the spectral range of the light signals guided in the wave guide 17 waveguide and in the spectral range of the light signals carried in the distribution waveguides 29 is largely transmissive, the circularly polarized light signals of both spectral ranges being linearly polarized after reflection or transmission. In the coupling waveguides 20 of the second coupling waveguide group 21 are thus each have a frequency component of the waveguides in the coupling 11 of the first coupling waveguide group 12 inputted light signals and the frequency components of the coupled into the coupling waveguide 27 of the third coupling waveguide group 28 light signals superimposed.

Fig. 7 shows a top view of an embodiment example of a device according to the invention for polarization-independent separation and superimposition of light signals having different frequency components, which has a waveguide chip 1 with a waveguide carrier layer 10 according to the aforementioned embodiments. In the waveguide carrier layer 10 , coupling waveguide 37 of a first coupling waveguide group 38 and coupling waveguide 39 of a second coupling waveguide group 40 are introduced, which open out on both sides of a first free-radiation region 41 which ends in a central filter gap 42 and inserted first polarization filter 43 as a polarization conversion element.

The exemplary embodiment according to FIG. 7 is equipped with a waveguide phase grating which is constructed from a first partial waveguide phase grating 45 having a phase shifting waveguide 44 and a second partial waveguide phase grating 47 having a phase shifting waveguide 46 . The each in the first free beam area 41 lead to the phase shifting waveguide 44 , 46 of the partial wave lenleiterphasengitter 45 , 47 are mutually opposite on both sides of the central filter gap 42 and are formed in each partial waveguide phase grating 45 , 47 in pairs with an optical length of different lengths.

The phase shifting waveguide 44 , 46 of the partial wave guide phase grating 45, 47 open out on both sides of the central filter gap 42 into a second free radiation area 48 , this being designed in accordance with the first free radiation area 41 . A second polarization filter 49 is introduced as a polarization conversion element in the second free jet region 48 in the transverse direction through the running central filter gap 42 . In the second free-jet region 48 of the second polarization filter furthermore open at both ends 49 coupling waveguide 50 of a third coupling waveguide array 51 and coupling waveguide 52 of a fourth coupling shafts conductor group 53, which terminate with their other ends to the second coupling side 22nd

The polarization filters 43, 49 of the apparatus of Fig. 7 are formed so that lenleiter in Koppelwel 39, 52 for example, the second coupling waveguide group 40 and the fourth coupling waveguide group 53 coupled linearly polarized light signals with their transverse electric components in the Phasenschiebewel lenleiter 44 of the first partial wave conductor phases grid 45 are transmitted while the transverse magnetic component is reflected and coupled into the phase shifting waveguide 46 of the second part of the waveguide phase grating 47 . After passing through the partial waveguide phase grating 45 , 47 , the transverse components of the light signals are again superimposed, for example, with reflection of the transverse magnetic component and transmission of the transverse electrical component in the other polarization filter 43 , 49 , and each apply a coupling waveguide 39 , with their individual frequency components. 52 of the second coupling waveguide group 40 or the fourth coupling waveguide group 53 .

The phase shifting waveguide 44 of the first part of the waveguide phase grating 45 and the phase shifting waveguide 46 of the second partial waveguide phase grating 47 are designed so that the transverse components carried in them are transmitted with equal losses, so that after the superimposition of the transverse electrical component and the transverse one -magnetic component has the same polarization direction as before the separation of the light signals. As a result, a largely polarization-independent transmission characteristic of the device according to FIG. 7 is achieved.

It is understood that with a corresponding configuration of the polarization filter 43 , 48 also the Kop pelwellenleiter 37 , 50 of the first Koppelwellenlei tergruppe 38 or the third Koppelwel lenleitergruppe 41 can be used accordingly.

In the coupling waveguide 37 of the first coupling waveguide group 38 or the coupling waveguide 50 of the third coupling waveguide group 51 , for example, light signals with only one transverse component can also be fed in, either into the phase shifting waveguide 44 of the first partial waveguide phase grating 45 or into the phase shifting waveguide 46 of the second partial waveguide phase grating 47 and after passing through the free beam areas 41 , 48, the coupling waveguides 37 , 50 of the other coupling pelwellenleitergruppe 38 , 51 act broken down into frequency components. As a result, the surface of the waveguide chip 1 is optimally used, even if certain losses occur in the latter transmission path.

Fig. 8 shows in cross section a part example of the first free jet region 26 of the embodiment according to FIG. 6, the remaining beam areas 33 , 41 , 48 divided by a central filter gap 31 , 42 being constructed accordingly. Into the waveguide carrier layer 10 completely crossing and into the substrate 9 into the middle filter gap 31 , the transmission filter 32 is inserted, which is composed of a number of dielectric layers 55 applied to a layer carrier 54 . The transmission filter 32 is connected to a curing upon irradiation with ultraviolet light, the adhesive 56 in the fixed Mittenfil terspalt 31 and fills this up from on edge-side adhesive substantially completely.

Fig. 9 shows in a representation corresponding to Fig. A modified embodiment, for example, of the first free-jet region 26 applied 8 with one on one wall side of the waveguide substrate layer 10 crossing center filtration gap 31 of several layers 55 constructed Transmissionsfil ter 32nd The transmission filter 32 is applied in the embodiment according to FIG. 9 with the so-called sputtering technique on one wall side of the central filter gap 31 , with a certain free space remaining on the opposite side of the central filter gap 31 , which is air-filled in the exemplary embodiment shown in FIG. 9 is. To avoid contamination and to reduce reflections, it is expedient to fill this free space, for example with a filler material that cures under irradiation with ultraviolet light.

It goes without saying that, due to the reversibility of the light paths, the exemplary embodiments of the device according to the invention can also be used for superimposing frequency components within a spectral range. For example, in the coupling waveguide 11 , 20 of the coupling waveguide groups 12 , 21 in the exemplary embodiment according to FIG. 2, individual, relatively closely spaced frequency components can also be fed in, which are polarization-independent over the waveguide phase grating 17 superimposed on one another in the other coupling waveguides 11 , 20 couple with a so-called multiplexer function.

Claims (12)

1. Device for polarization-independent separation and superimposition of different frequency components having light signals with Kop pelwellenleitern ( 11 , 20 , 27 , 34 , 37 , 39 , 50 , 52 ) which in at least one free beam area ( 14 , 18 , 26 , 33 , 41 , 48 ), with at least one waveguide phase grating, which has a number of phase shifting waveguides ( 16 , 44 , 46 ) each formed in pairs by an optical length and has a free beam area ( 14 , 18 , 26 , 33 , 41 , 48 ) opens, and with at least one polarization conversion element with which the polarization ratios of the light signals can be changed to achieve a polarization-independent transmission characteristic , characterized in that the or each polarization conversion element ( 15 , 19 , 32 , 36 , 43 , 49 ) in the optical Beam path of the respectively assigned free beam area ( 14 , 18 , 26 , 33 , 4 1 , 48 ) is arranged so that it can be acted upon with light signals between the coupling waveguides ( 11 , 20 , 27 , 34 , 37 , 39 , 50 , 52 ) and the phase-shifting wave guides ( 16 , 44 , 46 ). 2. Device according to claim 1, characterized in that two free beam areas ( 14 , 18 , 26 , 33 , 41 , 48 ) are provided, into which the phase shift waveguide ( 16 , 44 , 46 ) open, each free beam area ( 14 , 18th , 26 , 33 , 41 , 48 ) is assigned a polarization conversion element ( 15 , 19 , 32 , 36 , 43 , 49 ). 3. Apparatus according to claim 1 or 2, characterized in that the or each polarization conversion element is a polarization filter ( 43 , 49 ) with the transverse-electrical components and transverse-magnetic components of the light signals spatially separable be or can be combined. 4. The device according to claim 3, characterized in that. Waveguide phase grating partial waveguide phase grating ( 45 , 47 ), which are each set up for low-loss management of transverse magnetic components and transversal electrical components and have attenuations, each for guided transverse components are each the same. 5. Apparatus according to claim 1 or 2, characterized in that the or each polarization conversion element is a λ / 4 delay element ( 15 , 19 , 32 , 36 ). 6. The device according to claim 5, characterized in that the or each λ / 4 delay element ( 15 , 19 ) is reflective in at least one spectral range and for light signals in this spectral range the respective free beam range ( 14 , 18 , 26 , 33 ) limited. 7. The device according to claim 6, characterized in that the or each λ / 4 delay element ( 15 , 19 ) on an edge side of the assigned free radiation area ( 14 , 18 ) is brought up. 8. Device according to one of claims 1 to 6, characterized in that a distribution waveguide ( 25 ) is provided which in a free jet area. ( 18 ) opens. 9. Device according to one of claims 1 to 5, characterized in that distribution shaft conductors ( 29 ) are provided which open into a free beam area ( 26 , 33 ) and are each formed with the same optical length. 10. Device according to one of claims 1 to 5, 8 or 9, characterized in that the or each polarization conversion element ( 15 , 19 , 32 , 36 , 43 , 49 ) is arranged in a recess ( 24 , 31 , 42 ) which borders on at least one side to the assigned free jet area ( 14 , 18 , 26 , 33 , 41 , 48 ). 11. The device according to claim 10, characterized in that at least one Polarisationskon version element ( 15 , 19 , 32 , 36 , 43 , 49 ), the recess ( 24 , 31 , 31 , 42 ) is glued in substantially filling. 12. The device according to claim 10, characterized in that at least a Polarisationskon version element (15, 19, 32, 36, 43, 49) in sputtering technique at a to the associated free-radiating region (14, 18) adjoining the wall of the recess (24 ) is applied.