DE19756296A1 - Integrated transmitter-receiver circuit for an optical duplex system - Google Patents

Abstract

An integrated transmitting-receiving circuit (transceiver) designed as two complementary types for an optical duplex system with two light waves with different operating wavelengths to be transmitted in opposite directions via an optical fibre has a wavelength-independent optical switch designed as a Y structure formed of waveguide paths. The first path of the switch is designed as a connecting waveguide between the optical fibre and the two other paths, the second path leads to the transmission laser designed according to the complementary type for the corresponding operating wavelength, and the third path leads to a photodetector system with two photodetector sections optically connected in series, designed each for one of the two operating wavelengths and electrically independent of one another. The photodetector section designed for the shorter operating wavelength is arranged between the switch and the photodetector section designed for the longer operating wavelength.

Description

The invention relates to an integrated transmitter-receiver circuit (transceiver), which is provided in the form of two complementary types for an optical duplex system with two light waves to be transmitted in opposite directions via an optical fiber with different operating wavelengths (λ ₁ <λ ₂ ) and whose transmission lasers and photodetectors are constructed on the basis of III-V materials with different transmission or absorption properties with respect to the two operating wavelengths, the complementary type that transmits on the operating wavelength λ ₁ and receives on the operating wavelength λ ₂ , one in Contains series with the photodetector absorber section.

Such arrangements of two complementary types are described in US Pat. Nos. 5,031,188 and 5,144,637. These are circuit structures in which the laser and the photodetector are arranged in series on a waveguide path. In the series connection according to US Pat. No. 5,031,188, λ _send <λ _receive , ie the received light wave must pass the laser on the way to the photodetector. An absorber section is provided between the laser and the photodetector in order to reduce the power level of the laser in the photodetector. In this section, the wavelength emitted by the laser is almost absorbed; however, the absorber section is transparent to the incident wavelength to be detected by the photodetector. Due to the series connection, the "full" laser power hits the photodetector. The complementary type of the transceiver shown in U.S. Patent 5,031,188 is described in U.S. Patent 5,144,637. In this in-line transmitter-receiver arrangement, in which λ _send <λ _reception , the light wave from the optical fiber enters the waveguide on the receiver side and acts on the photodetector. The relatively high transmission power of the laser is coupled into the optical fiber via the waveguide and also a photodetector arranged in series. However, the small residual sensitivity of the photodetector to the transmission signal can interfere with the reception function due to the high transmission level.

Even if the material of the laser for the wavelength of the received Light wave is almost transparent, this transparency is nevertheless through the influences the injection current of the laser generating the modulation signal. Therefore, such transceiver arrangements have to be complex Countermeasures against such interference in the form of Push-pull modulation and external differential amplifiers for improvement crosstalk attenuation. Nevertheless, it remains Crosstalk attenuation too great for practical use.

DE-A 195 48 547 describes an integrated transceiver Arrangement in which the light wave emitted by a laser has a different wavelength than the light wave that passes through a fiber on the Transmitter-receiver arrangement transmitted and from a photodetector Will be received. Here too there is the problem of reducing stray light from the laser to the photodetector. That will be after the mentioned State of the art achieved by selectively highly reflective Bragg gratings. Furthermore, the transmitter-receiver arrangement for the suppression of Scattered light-absorbing means outside of the light wave leading Waveguide. With this arrangement, the crosstalk from the laser can reduce the photodetector to less than -30 dB, but in practice is not sufficient in many cases. In addition, the spatial Expansion relatively large, which makes the production not inexpensive can be done.

In one the same transmitter-receiver arrangement as DE-A 195 48 547 relevant article by Heidrich et al. "Bi-Directional Photonic Integrated Transceivers for Optical Communication Systems "in SPIE Proc. Series, Vol. 2953, Broadband Strategies and Technologies for Wide Area and Local Access Networks, Oct. 1996, Berlin / D, pp. 149-156, 1996 mentions that in addition to the Bragg gratings that act as filters, a waveguide layer, e.g. B. from GaInAsP, is provided in front of the photodetector, which one Bandgap equivalent to a wavelength of 1.4 µm and has residual light  the wavelength emitted by the laser absorbs 1.3 µm, but for the received signal is transparent at a wavelength of 1.5 µm. This transceiver arrangement also has a relatively large spatial area Expansion.

According to the prior art, no circuit is known that both a low crosstalk and high bit rates with high sensitivity of the Photodetector and small spatial dimensions of the component Allows chips.

It is therefore an object of the invention to provide a transmitter-receiver circuit to be specified, which simultaneously meets the requirements mentioned.

The task is carried out by an integrated transmitter-receiver circuit initially mentioned type in that according to the invention the Transceiver a wavelength-independent optical switch in the form of a have Y structure formed from waveguide paths, the first path the switch as a connecting waveguide between the optical fiber and the the other two paths is formed, the second path to the transmission laser leads, each corresponding to the complementary type on the associated Operating wavelength is designed, and the third path to one Photodetector arrangement with two optically in series, each on one of the two operating wavelengths and designed electrically from each other leads independent photodetector sections, of which those for the smaller Operating wavelength trained photodetector section between the switch and that designed for the longer operating wavelength Photodetector section is arranged.

The transmitter-receiver circuit according to the invention, which is a simple, has a wavelength-independent, compact Y structure, enables at small spatial extent such a structure of each complementary type, which differs only in the broadcast part. On the other hand the receiving parts can be constructed in both complementary types after be identical. The desired function, namely one of the two Receiving operating wavelengths is achieved in that the Photodetector section is controlled for that to be received Wavelength is formed.  

In order to optimally adapt the current account and depending on the application to increase the sensitivity of the photodetector arrangement is the optical one Crossover in Y structure with a symmetrical or asymmetrical Power sharing / unification regarding the 2nd and 3rd waveguide path educated.

Due to the Y structure of the circuit according to the invention with the Transmitting and receiving part arranged parallel to one another on the Y structure only the extremely small one is reflected by the anti-reflective chip edge and at the Y-turnout the laser light is reduced by 50% Interference signal passed to the photodetector.

In embodiments of the invention, depending on Purpose to design the photodetector arrangement such that on the one hand the photodetector arrangement one on the larger one Operating wavelength optimized photodetector and one Upstream photodetector, optimized for the lower wavelength Absorber section or the photodetector arrangement on the other the smaller operating wavelength has optimized photodetector. This Embodiments of the invention allow the increase if necessary the sensitivity of the operating wavelength to be received designed photodetector. In the latter embodiment, can the layer sequences arranged between the substrate and the contact layer also to be extended to such a lateral extent that that of the the first-mentioned embodiment corresponds to the manufacturing process effective for the same extent for the photodetector arrangements in terms of masking.

The layers necessary for the realization of the photodetector function in an epitaxial growth step with the corresponding Sequence of waveguides applied.

Further details of the invention and its advantageous Embodiments are related to the following Description of the figures explained in more detail.  

Show:

Fig. 1 shows the schematic construction of an embodiment comprising a two photodetector sections photodetector array on a waveguide path and a laser transmitter on another waveguide path for λ _T1 <λ _R2;

Fig. 2 _T2 the schematic structure of the same embodiment, now for λ _R1 <λ;

Fig. 3 shows the layer structure of a two photodetector sections photodetector array;

Fig. 4 shows the layer structure of a photodetector array, comprising an optimized to the larger operating wavelength photodetector and a photodetector this upstream to the lower wavelength, optimized absorber section;

Fig. 5 shows the layer structure of a photodetector array, comprising an optimized to the smaller operating wavelength photodetector

Fig. 6 shows the schematic construction of a transmitter-receiver circuit according to the invention with getapertem connection waveguide and a photodetector arrangement in accordance with Fig. 4;

Fig. 7 is a schematic representation of an optical bi-directional "Full Service Access Network (FSAN)" with distribution function up to 1: 32, and complementary transceivers;

Fig. 8 is a schematic representation of an optical, bidirectional point-to-point connection with complementary transceivers.

In Fig. 1, a transmitter-receiver circuit according to the invention is for _transmitting λ <λ _reception, shown, in which the first waveguide path of the Y-shaped switch is designed as a connection waveguide between the optical fiber and the other two paths. The second path leads to a transmission laser L ₁ , which emits light waves on the wavelength λ _T1 (1.3 μm), which are to be received in the complementary transceiver (not shown here). In the photodetector arrangement shown in FIG. 1, which is guided on the third waveguide path and consists of two optically arranged photodetector sections, the photodetector section PD _{1 designed} for the smaller operating wavelength is arranged between the switch and the photodetector section PD _{2 designed} for the longer operating wavelength . If the light waves transmitted by the transmitter laser of the complementary transceiver are to be received with the longer operating wavelength, the photodetector section PD _{2 is} activated and receives on the wavelength λ _R2 ; the photodetector section PD ₁ is not activated and then acts as an absorber section for light waves with the smaller operating wavelength. The absorber section is transparent to the (longer) operating wavelength to be received.

FIG. 2 shows the transceiver λ _send <λ _receive that is complementary to FIG. 1. This transceiver now leads on its second path the transmission laser L ₂ , which emits light waves with the wavelength λ _T2 . In this case, the photodetector section PD _{1 is} activated in the photodetector arrangement and receives the light waves with the smaller wavelength λ _R1 .

FIG. 3 shows the layer structure of a photodetector array of the transmitter-receiver circuit according to the invention, consisting of the photo detecting sections PD ₁ and PD _2, wherein the photodetector section PD _1, the photo detecting section PD ₂ is formed for the greater wavelength of operation for the smaller wavelength of operation and. A layer waveguide 31 and a waveguide rib 32 formed on the layer waveguide 31 are applied to a substrate 30 . The refractive indices of the layered waveguide 31 and the waveguide rib 32 are larger than the refractive index of the material lying under the waveguide in order to guarantee the waveguide. A first n⁺-doped absorber layer 33 and a second undoped absorber layer 34 with the same band gap as the absorber layer 33 are arranged on the layer waveguide 31 . Both absorber layers 33 , 34 are formed from semiconductor materials which have larger refractive indices than the materials of layer waveguide 31 and waveguide rib 32 . The bandgap of the absorber layers 33 and 34 are smaller than the photon energy of the light wave with the smaller operating wavelength and larger than the photon energy of the light wave with the longer operating wavelength. For the formation of the first photodiode section PD ₁ , a p⁺ region 36 is now diffused into part of the undoped absorber layer 34 and provided with a metal contact layer 37 . For the formation of the second photodetector section PD ₂ , a further undoped absorber layer 35 is applied to the remaining surface of the absorber layer 34 , into which a p⁺ region 38 also diffuses and which is provided with a metal contact layer 39 . The band gap of the absorber layer 35 is smaller than the photon energy of the light wave with the longer operating wavelength. Finally, a passivation layer is applied to the layers not covered by contacts 37 and 39 .

If the photodetector section PD ₂ is now controlled via the contact 39 and the absorber layer 33 , which is simultaneously formed as an n⁺ contact layer, the light which acts as a stray light for this section is absorbed with the smaller operating wavelength λ _R1 in the uncontrolled section PD ₁ , while this Section for the larger operating wavelength λ _{R2 is} transparent. This signal is thus detected in the photodetector section PD ₂ (solid thick line).

If the signal with the smaller operating wavelength λ _{R1 is to be} detected (dashed thick line), the contact 37 and the absorber layer 33 designed as an n⁺ contact layer must be activated. Light waves with the longer operating wavelength λ _R2 , the photon energy of which is smaller than the bandgap of the material of the absorber layers 33 and 34 , pass through the photodetector section PD ₁ into the area of the non-activated photodetector section PD ₂ , without being detected by the activated photodetector section PD ₁ . To further improve the crosstalk attenuation, a rear-side absorber layer 30.0 can be applied on the side of the substrate 30 facing away from the transmitter-receiver circuit, which absorbs the scattered light occurring there.

The embodiments according to the invention are shown in the following figures a photodetector arrangement, comprising one on the larger one Operating wavelength optimized photodetector and one Upstream photodetector, optimized for the lower wavelength Absorber section and only one on the smaller one Operating wavelength optimized photodetector, shown in the layer structure.

Thus, Fig. 4 shows an optimized to the greater operating wavelength photodetector section PD ₂ with upstream in series absorber section AS for the smaller operating wavelength. The layer sequence already described for FIG. 3 (substrate 40 , rear side absorber layer 40.0 layer waveguide 41 , rib waveguide 42 ) is also the same in this embodiment up to the first absorber layer 43 , which is simultaneously formed as an n⁺-contact layer, for 1.4 μm. In this embodiment, the absorber layer 43 is followed by an intrinsic semiconductor layer 44 of a quaternary mixed crystal based on InP with a band gap, corresponding to a vacuum wavelength of 1.6 μm, for example GaInAsP, or a ternary mixed crystal based on InP with a band gap, corresponding to a vacuum wavelength of 1.65 µm, for example GaInAs. A cover layer 45 (eg InP) has also grown on the layer 44 , which is an absorber layer for the useful signal of the photodetector section PD ₂ . A p-region 48 is diffused into this cover layer 45 and provided with a metal contact 49 . The material transfer from layers 45 and 44 in this case facilitates the setting of the diffusion depth of area 48 . A passivation layer 46 closes off the circuit arrangement described above (with the exception of the metal contact 49, of course ). The mode of operation of the described photodetector arrangement is the same as that described for FIG. 3 if the photodetector section PD _{2 is} activated there.

For the layer sequence shown in FIG. 5 of a photodetector section PD ₁ optimized for the smaller operating wavelength, the mode of operation has already been described for FIG. 3 if the photodetector section PD _{1 is} activated there. On substrate 50 with rear-side absorber layer 50.0 , layer waveguide 51 , ribbed waveguide 52 , absorber layer 53 designed as an n⁺-contact layer is an absorber layer 54 for the useful signal to be received λ _R1 = 1.3 μm (thick dashed line), made of an intrinsic semiconductor material a band gap, corresponding to a vacuum wavelength of 1.4 µm. As described in relation to FIG. 4, a cover layer 55 , for example InP, has grown onto the layer 54 , into which a p-region 58 has diffused and is provided with a metal contact 59 . Again, a passivation layer 56 - analogous to FIG. 4 - is finally arranged.

The embodiments shown in FIGS. 4 and 5 with an optimized photodetector section and an optimized absorber section ensure, compared to the embodiment shown in FIG. 3, an improvement in the sensitivity of the detector for the reception of the useful signal and an optimal absorption of the interference signal.

For the layer sequence shown in FIGS. 3 and 4, the material of the shorter upper absorber layer is a quaternary or ternary mixed crystal based on InP with a band gap corresponding to a vacuum wavelength of 1.6 μm (quaternary) or 1.65 μm (ternary), for example a GaInAsP mixed crystal or a GaInAs mixed crystal. The lower continuous absorber layer in these layer sequences is formed from a quaternary mixed crystal based on InP with a band gap corresponding to a vacuum wavelength of 1.4 µm. The two lower continuous absorber layers of the exemplary embodiments shown in FIGS . 3 and 5 are also formed from such a mixed crystal with the band gap mentioned, for example GaInAsP.

Fig. 6 shows the schematic structure of the entire transmitter-receiver circuit with taped connection waveguide in perspective. The ribbed waveguide 62 is applied to the layer waveguide 61 as a wavelength-independent optical switch and is Y-shaped. The first waveguide path 62.1 is tapered as a connecting waveguide to the optical fiber, in order to achieve a low coupling attenuation by means of optical field adaptation through adiabatic field transformation between the waveguide field and the light guide field. The second waveguide path 62.2 guides the transmission laser L ₁ and the third, 62.3 , a photodetector arrangement consisting of an absorber section AS and a photodetector section PD ₂ according to FIG. 4.

The following are intended for the specific embodiment of the invention Embodiments are mentioned.

To avoid leakage currents, the pn junction in the Photodetector sections created by area-selective p-diffusion. As a result, there is no pn transition in the mesa flanks Semiconductor material of the absorber layer with the small band gap for that respective useful signal.

The contacts of the photodetector section PD ₁ and PD ₂ are led upwards, so that doping of the layer waveguide and the waveguide rib is not necessary.

When using a semi-insulating substrate, the electrical High frequency properties of the photodetector sections improved.

A high level of coupling from the waveguide to the interference signal absorber layer To achieve this, the absorber section is designed to be multimodal.

It has been shown that in the transceiver according to the invention Circuit with a simple, compact Y structure at a length of Absorber section of 0.2 mm already crosstalk for the light the wavelength of 1.3 µm of 45 dB can be achieved by additional Measures, for example by separating the transmitter laser and Photodetector arrangement by means of an outside of these components leading waveguide paths arranged optical absorber, further can be improved. This optical absorber does not suppress this light guided along the waveguide paths.

In the case of a "Full Service Access Network (FSAN)" according to FIG. 7, a central station 70 , which is equipped with a transceiver T ₁ -R ₂ , sends identical information to a plurality, here 32 subscriber stations 75.01 to 75.32 , on an operating wavelength λ _T1 that arrive at the subscriber stations 75.01 to 75.32 on the same operating wavelength, now there as the reception wavelength λ _R1 . All transceivers T ₂ -R _{1 of} the subscriber stations 75.01 to 75.32 are equipped with identical circuits.

The transmission network between the central station 70 and the subscriber stations 75.01 to 75.32 is constructed as a "passive optical network (PON)" and contains an optical fiber 72 between the central station 70 and a passive optical star coupler 73 in which the transmission part T _{1 of} the transceiver of the central station 70 transmitted information is evenly distributed over 32 optical fibers 74.01 to 74.32 , which connect the star coupler 73 with the subscriber stations 75.01 to 75.32 . This division ratio 1:32 in the passive star coupler 73 is, for. B. brought about by optical 3 dB crossovers in five cascaded stages. Including the power division in transceiver switches 71 and 76.01 to 76.32 with 3 dB each and the attenuation of about 9 dB on the light waves guided via the optical fiber 72 and the respective optical fiber 74.01 to 74.32 , the power of the light wave emitted by the central station 70 is reduced as a result of the power division 1:32 in the star coupler 73 in five stages until the light wave to be received reaches the respective subscriber station 75.01 to 75.32 , again by 5 × 3 dB = 15 dB, that is to say a total of 30 dB. Since the sensitivity of a photodetector R ₁ is said to be an order of magnitude higher than an interference signal emanating from its own transmission laser T ₂ , a transceiver with a high-performance transmission laser, transmission power z. B. 1 mW, and a sensitive photodetector, sensitivity z. B. 0.001 mW to equip.

The relationships with regard to the performance requirements previously explained for the transmission direction from the central station 70 to a subscriber station 75.01 to 75.32 (downward direction or "downstream") also apply analogously to the opposite transmission direction (upward direction or "upstream"). In the upward direction, however, a different operating wavelength than in the downward direction is used and, moreover, the individual subscriber stations 75.01 to 75.32 z. B. provided in time division multiplex.

For the two operating wavelengths, for. B. the so-called 2nd optical window, 1.3 microns, and the so-called 3rd optical window, 1.5 microns, used. For a FSAN, the 3rd optical window can be set for the downward direction or vice versa. The number of complementary transceivers T ₁ -R ₂ or T ₂ -R ₁ in the central station 70 and the subscriber stations 75.01 to 75.32 behaves like the division ratio in the passive optical star coupler 73 .

In the case of a point-to-point connection according to FIG. 8, the information to be transmitted is transmitted from the transmitting part T _{1 of} the transceiver 80.1 with the wavelength λ _T1 via the optical fiber 81 to the transceiver 80.2 , which has a receiving part R ₁ for this wavelength. From the transceiver 80.2 , which has a transmitting part T ₂ , a light wave with the wavelength λ _{T2 is} transmitted via the optical fiber 81 to the transceiver 80.1 and received by the receiving part R ₂ . The receiving parts R ₁ , R _{2 of} the two transceivers 80.1 and 80.2 are formed according to the invention from two optically arranged photodetector sections R ₁ / R ₂ , one of which is designed for one of the two operating wavelengths. In each case the photodetector section is switched, which is designed for the wavelength of the light wave to be received, so R ₁ in the transceiver 80.2 for the reception of light waves with λ _T1 and R ₂ in the transceiver 80.1 for the reception of light waves with λ _T2 in the corresponding reverse direction . An optimization of the photodetector sections and associated increased technological effort is not necessary for this application, since no power division - except in transceiver switches 82.1 , 82.2 - has to be considered.

Claims (21)

1. Integrated transmitter-receiver circuit (transceiver), which is provided in the form of two complementary types for an optical duplex system with two light waves to be transmitted in opposite directions via an optical fiber with different operating wavelengths (λ ₁ <λ ₂ ) and their transmitter lasers and photodetectors on the basis of III-V materials with different transmission or absorption properties with respect to the two operating wavelengths are constructed as a layer packet on a substrate, the complementary type which transmits on the operating wavelength λ ₁ and receives on the operating wavelength λ ₂ , a in Contains the series with the photodetector absorber section, characterized in that the transceivers have a wavelength-independent optical switch in the form of a Y structure formed from waveguide paths , wherein

• the first path of the switch is designed as a connecting waveguide between the optical fiber and the other two paths,
• - The second path leads to the transmission laser (L ₁ or L ₂ ), which is designed according to the complementary type in accordance with the associated operating wavelength, and
• - The third path to a photodetector arrangement with two optically lying in series, each designed on one of the two operating wavelengths and electrically independent of each other photodetector sections (PD ₁ , PD ₂ ), of which the photodetector section designed for the smaller operating wavelength between the switch and for the larger operating wavelength trained photodetector section is arranged.

2. Transmitter-receiver circuit according to claim 1, characterized in that each alternatively that photodetector section is controlled that for the receiving wavelength is formed. 3. Transmitter-receiver circuit according to claim 1, characterized in that  the optical crossover in a Y structure with a symmetrical power split / union is formed with respect to the 2nd and 3rd waveguide paths. 4. Transmitter-receiver circuit according to claim 1, characterized in that the optical crossover in Y structure with an asymmetrical Power sharing / unification regarding the 2nd and 3rd waveguide path is trained. 5. Transmitter-receiver circuit according to claim 1, characterized in that the photodetector arrangement has a photodetector section (PD ₂ ) optimized for the larger operating wavelength and one upstream of this photodetector section (PD ₂ ) has an absorber section (AS) optimized for the lower wavelength. 6. Transmitter-receiver circuit according to claim 1, characterized in that the photodetector arrangement has a photodetector section (PD ₁ ) which is optimized for the smaller operating wavelength. 7. Transmitter-receiver circuit according to at least one of the preceding claims, characterized in that the photodetector sections (PD ₁ , PD ₂ ) and the absorber section (AS) have a layer waveguide ( 31 or 41 or 51 ) with a waveguide rib ( 32 or 42 or 52 ) exhibit. 8. Transmitter-receiver circuit according to claim 1 or claim 5 or claim 6, characterized in that the photodetector arrangement has two superimposed absorber layers, of which the lower ( 43 ) consists of a semiconductor material which is the smaller of the two operating wavelengths (λ _R1 ) is absorbed and extends over the entire length of the photodetector arrangement, and the upper absorber layer ( 44 ) is designed for the longer of the two operating wavelengths and only extends over the photodetector section (PD ₂ ) which is used for the detection of the light wave with the longer operating wavelength ( λ _R2 ) is provided. 9. Transmitter-receiver circuit according to claim 8, characterized in that
the lower continuous absorber layer ( 43 ) of the photodetector section (PD ₁ ) designed for the detection of the signals with the smaller operating wavelength is formed from a semiconductor material whose refractive index is greater than the refractive index of the transparent waveguide material of the layer waveguide ( 31 or 41 or 51 ) and Waveguide rib ( 32 or 42 or 52 ) and which has a band gap which is smaller than the photon energy of the photons of the interference signal and larger than the photon energy of the incoming useful signal to be detected by the photodetector section (PD ₁ ) and
the shorter upper absorber layer ( 35 or 44 ), which extends only over the second photodetector section (PD ₂ ), is formed from a semiconductor material whose refractive index is greater than the refractive index of the transparent waveguide material of the layer waveguide ( 31 or 41 or 51 ), the waveguide rib ( 32 or 42 or 52 ) and the absorber material ( 43 ) for the shorter wavelength and which has a band gap which is smaller than the photon energy of the incoming useful signal to be detected. 10. Transmitter-receiver circuit according to at least one of claims 1, 5, 8 and 9, characterized in that the shorter upper absorber layer ( 35 , 44 ) for the operating wavelengths in the 1.3 µm or 1.5 µm wavelength window. is formed from a quaternary mixed crystal based on InP with a band gap corresponding to a vacuum wavelength of 1.6 µm. 11. Transmitter-receiver circuit according to claim 10, characterized in that the InP-based quaternary mixed crystal is a GaInAsP mixed crystal. 12. Transmitter-receiver circuit according to one of claims 1, 5, 8, and 9, characterized in that the shorter upper absorber layer ( 35 , 44 ) for the operating wavelength in the 1.3 µm or 1.5 µm wavelength window. is formed from a ternary mixed crystal based on InP with a band gap corresponding to a vacuum wavelength of 1.65 µm. 13. Transmitter-receiver circuit according to claim 12, characterized in that the InP-based ternary mixed crystal is a GaInAs mixed crystal. 14. Transmitter-receiver circuit according to one of claims 1, 5, 8, and 9, characterized in that the lower continuous absorber layer ( 33 or 43 ) for the operating wavelength in the 1.3 µm or 1.5 µm wavelength window. is formed from a quaternary mixed crystal based on InP with a band gap corresponding to a vacuum wavelength of 1.4 µm. 15. Transmitter-receiver circuit according to claim 1 or claim 6, characterized in that for the operating wavelengths 1.3 µm or 1.5 µm wavelength window, the lower continuous absorber layer package ( 33 , 34 or 53 , 54 ) from a quaternary Mixed crystal based on InP is formed with a band gap corresponding to a vacuum wavelength of 1.4 µm. 16. Transmitter-receiver circuit according to claim 14 or claim 15, characterized in that the InP-based quaternary mixed crystal is a GaInAsP mixed crystal. 17. Transmitter-receiver circuit according to at least one of the preceding claims, characterized in that the absorber section (AS) is designed multimodal. 18. Transmitter-receiver circuit according to at least one of the preceding claims, characterized in that the pn junction in the photodetector sections (PD ₁ , PD ₂ ) is generated by means of area-selective p-diffusion. 19. Transmitter-receiver circuit according to at least one of the preceding claims, characterized in that the contacts ( 37 , 39 , 49 , 59 and 33 , 43 , 53 ) of the photodetector sections (PD ₁ and PD, respectively) optimized to one of the two operating wavelengths ₂ ) are led upwards. 20. Transmitter-receiver circuit according to at least one of the preceding claims, characterized in that a rear-side absorber layer ( 30.0 , 40.0 , 50.0 ) is arranged on the side of the substrate ( 30 , 40 , 50 ) facing away from the contacts . 21. Transmitter-receiver circuit according to at least one of the preceding claims, characterized in that the first path ( 62.1 ), designed as a connecting waveguide, of the switch is formed in a tapered shape in a Y structure.