We analyse the carrier-to-noise ratio of a millimeire-wave photonic link, demonstrating noise reduction by the use of a simple, fibrebased delay compensation element.
我们分析了毫米波光子链路的载波噪声比，展示了通过使用简单的基于光纤的延迟补偿元件来降低噪声。
{"title":"Noise Reduction For Photonic Millimetre-wave Signal Distribution","authors":"R. Griffin, S.L. Zhang, P. Lane, J. O'Reilly","doi":"10.1109/MWP.1997.740275","DOIUrl":"https://doi.org/10.1109/MWP.1997.740275","url":null,"abstract":"We analyse the carrier-to-noise ratio of a millimeire-wave photonic link, demonstrating noise reduction by the use of a simple, fibrebased delay compensation element.","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124483682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present results on superlattice oscillators for optical to mm-wave conversion which show that this new component is a good candidate for indoor wireless communications. The optical synchronisation is study theorically, and we present for the first time direct injection locking with wide locking bandwidth.
{"title":"Direct Optical Injection Locking Of Superlattice Millimetre-wave Oscillators","authors":"D. Tanguy, E. Penard, P. Legaud, C. Minot","doi":"10.1109/MWP.1997.740235","DOIUrl":"https://doi.org/10.1109/MWP.1997.740235","url":null,"abstract":"We present results on superlattice oscillators for optical to mm-wave conversion which show that this new component is a good candidate for indoor wireless communications. The optical synchronisation is study theorically, and we present for the first time direct injection locking with wide locking bandwidth.","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122782868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Optical modulators with very wide electrical bandwidths are essential components for optical control of microwaves and millimeter waves as well as high speed optical communication systems. It is possible to use different technologies to realize such components. LiNbO3 offers mature technology but suffers from a large index difference between optical and microwave frequencies, drift and low optical damage threshold. Polymers are promising canditates but their technology is immature and they have temperature stability difficulties. On the other hand compound semiconductors offer a mature material and processing technology. Among the compound semiconductor modulators electroabsoption modulators have demonstrated electrical bandwidths approaching 50 GHz with low drive voltages. For such devices electrical bandwidth is limited by the capacitance of the device. For low voltage operation upper limit seems to be around 40 GHz. For higher bandwidths electmoptic modulators utilizing traveling wave designs are the most promising candidates [ 11. In such a design electrode is designed as a transmission line. Therefore, electrode capacitance is distributed and does not limit the modulator speed. Modulating electrical signal on the electrode travel in the same direction as the modulated optical signal. If they travel with the same velocity the phase change induced by the electrical signal is integrated along the length of the electrode. Since the electrode capacitance is not the bandwidth limit one can make the electrode very long, typically thousands of wavelengths. This allows even a very small phase change over a wavelength to accumulate to an appreciable value. Therefore, drive voltage requirements can be significantly relaxed without sacrificing electrical bandwidth.
{"title":"Ultra Wide Bandwidth Traveling Wave Modulators In GaAs/AlGaAs","authors":"N. Dagli","doi":"10.1109/MWP.1997.740236","DOIUrl":"https://doi.org/10.1109/MWP.1997.740236","url":null,"abstract":"Optical modulators with very wide electrical bandwidths are essential components for optical control of microwaves and millimeter waves as well as high speed optical communication systems. It is possible to use different technologies to realize such components. LiNbO3 offers mature technology but suffers from a large index difference between optical and microwave frequencies, drift and low optical damage threshold. Polymers are promising canditates but their technology is immature and they have temperature stability difficulties. On the other hand compound semiconductors offer a mature material and processing technology. Among the compound semiconductor modulators electroabsoption modulators have demonstrated electrical bandwidths approaching 50 GHz with low drive voltages. For such devices electrical bandwidth is limited by the capacitance of the device. For low voltage operation upper limit seems to be around 40 GHz. For higher bandwidths electmoptic modulators utilizing traveling wave designs are the most promising candidates [ 11. In such a design electrode is designed as a transmission line. Therefore, electrode capacitance is distributed and does not limit the modulator speed. Modulating electrical signal on the electrode travel in the same direction as the modulated optical signal. If they travel with the same velocity the phase change induced by the electrical signal is integrated along the length of the electrode. Since the electrode capacitance is not the bandwidth limit one can make the electrode very long, typically thousands of wavelengths. This allows even a very small phase change over a wavelength to accumulate to an appreciable value. Therefore, drive voltage requirements can be significantly relaxed without sacrificing electrical bandwidth.","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126103707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In fibre optic TTD, the required time delay is achieved by transmitting the modulated optical carrier through an appropriate length of fiibre. Different time delays can be achieved by switching the optical carrier through various lengths of fibre. Alternatively, the time delay can be achieved using a series of Bragg grating reflectors in a single optical fibre. The wavelength selected at the tunable source corresponds to reflection from only one of the gratings introducing variable time delay (figure l )~.
{"title":"Evaluation of Bragg Fibre Gratings As TTD Elements in Optical Phased Array Systems","authors":"B. Smith, M. Nawaz","doi":"10.1109/MWP.1997.740263","DOIUrl":"https://doi.org/10.1109/MWP.1997.740263","url":null,"abstract":"In fibre optic TTD, the required time delay is achieved by transmitting the modulated optical carrier through an appropriate length of fiibre. Different time delays can be achieved by switching the optical carrier through various lengths of fibre. Alternatively, the time delay can be achieved using a series of Bragg grating reflectors in a single optical fibre. The wavelength selected at the tunable source corresponds to reflection from only one of the gratings introducing variable time delay (figure l )~.","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126566069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Wiedenmarin, C. Jung, M. Grabherr, W. Schmid, G. Reiner, K. Splitthof, R. Michalzik, K. Ebeling
The temporally resolved emission of an electrically biased vertical caviw surface emitting laser (VCSEL) after perturbation with a short optical pulse has been measured with a high resolution up-conversion setup. Transverse multimode devices show very fast oscillations of the laser emission at frequencies corresponding to the lateral mode spacing. Introduction Vertical-cavity lasers are predestined devices for high speed optical communications. The small cavity volume of VCSELs promotes high photon densities and therefore high resonance frequencies of the devices. There are some reports on ultrafast oscillations in VCSELs with frequencies exceeding 50 GHz [1,2]. Normally they are attributed to ultrafast relaxation oscillations based on the oscillatory energy transfer between the electronic and the photonic system. But they are far beyond measurements of relative intensity noise (RIN) and small signal modulation [3]. In this paper we present results on investigations of the transient response of a running VCSEL to a perturbation of the intrinsic photon density. Our investigations are restricted to perturbations with pulses having the same photon energy as the VCSEL in order to get no transient carrier heating caused by carrier-carrier scattering. Laser Structure We investigate VCSELs with 3 I~.2Gao.8As/GaAs quantum wells emitting in the 980 nm wavelength regime [4]. The devices are grown on n-doped GaAs substrate, which is transparent for the emission wavelength of the device. Therefore an optical pulse with a center wavelength equal to the emission wavelength of the VCSEL can be coupled through the substrate into the active region. Current is injected through a ring contact on top of the device and through the substrate. Current confinement is achieved either through proton-implantation in the top mirror or through selective oxidation of a thin AlAs layer after mesa etching. The optical fields of the proton-implanted devices are gain and thermally induced index guided, whereas the oxidized devices are mainly index guided by the oxide aperture. Measurement Setup Fig1 shows the measurement setup. The sample is mounted such that a 100 fs pulse from a titanium sapphire (Ti:Sp) laser is coupled fiom the substrate side into the VCSEL cavity, and the device luminescence is monitored at the epitaxial side. In this setup we have the advantage that the intense backscattered light fiom the mirror of the VCSEL does not cause problems in the detection system. The laser luminescence can be measured either by an optical sampling scope with a time resolution of 25 ps or by up-conversion [5,6]. For that purpose the VCSEL output and a fraction of the Ti;Sp pulse are collimated on a crystal and mixed using type I phasematching. The polarization plane of the linearly polarized Ti:Sp pulse can be rotated
{"title":"Measurement Of Ultrafast Oscillations In Vertical Cavity Lasers After Pulse Perturbation","authors":"D. Wiedenmarin, C. Jung, M. Grabherr, W. Schmid, G. Reiner, K. Splitthof, R. Michalzik, K. Ebeling","doi":"10.1109/MWP.1997.740281","DOIUrl":"https://doi.org/10.1109/MWP.1997.740281","url":null,"abstract":"The temporally resolved emission of an electrically biased vertical caviw surface emitting laser (VCSEL) after perturbation with a short optical pulse has been measured with a high resolution up-conversion setup. Transverse multimode devices show very fast oscillations of the laser emission at frequencies corresponding to the lateral mode spacing. Introduction Vertical-cavity lasers are predestined devices for high speed optical communications. The small cavity volume of VCSELs promotes high photon densities and therefore high resonance frequencies of the devices. There are some reports on ultrafast oscillations in VCSELs with frequencies exceeding 50 GHz [1,2]. Normally they are attributed to ultrafast relaxation oscillations based on the oscillatory energy transfer between the electronic and the photonic system. But they are far beyond measurements of relative intensity noise (RIN) and small signal modulation [3]. In this paper we present results on investigations of the transient response of a running VCSEL to a perturbation of the intrinsic photon density. Our investigations are restricted to perturbations with pulses having the same photon energy as the VCSEL in order to get no transient carrier heating caused by carrier-carrier scattering. Laser Structure We investigate VCSELs with 3 I~.2Gao.8As/GaAs quantum wells emitting in the 980 nm wavelength regime [4]. The devices are grown on n-doped GaAs substrate, which is transparent for the emission wavelength of the device. Therefore an optical pulse with a center wavelength equal to the emission wavelength of the VCSEL can be coupled through the substrate into the active region. Current is injected through a ring contact on top of the device and through the substrate. Current confinement is achieved either through proton-implantation in the top mirror or through selective oxidation of a thin AlAs layer after mesa etching. The optical fields of the proton-implanted devices are gain and thermally induced index guided, whereas the oxidized devices are mainly index guided by the oxide aperture. Measurement Setup Fig1 shows the measurement setup. The sample is mounted such that a 100 fs pulse from a titanium sapphire (Ti:Sp) laser is coupled fiom the substrate side into the VCSEL cavity, and the device luminescence is monitored at the epitaxial side. In this setup we have the advantage that the intense backscattered light fiom the mirror of the VCSEL does not cause problems in the detection system. The laser luminescence can be measured either by an optical sampling scope with a time resolution of 25 ps or by up-conversion [5,6]. For that purpose the VCSEL output and a fraction of the Ti;Sp pulse are collimated on a crystal and mixed using type I phasematching. The polarization plane of the linearly polarized Ti:Sp pulse can be rotated","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129246216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is well known that the RF performance of optical fiber links falls short of what is desired, and often required. These seem to be the facts of life: links using colmmercially available components have at least 20 dB of RF loss, their noise figures are even greater than their loss, and their dynamic ranges are marginal to acceptable [ 11. Further, all three of these performance parameters degrade significantly with increasing frequency. This sitate of affairs is in stark contrast with the fundamental limits of link performance [2], which have shown that low loss, low noise figure, high linearity links should be possible, even up to fairly high frequencies. So why have we not been able to realize links with such performance? We will pursue the answer to this question by hypothesizing a set of link requirements and seeing what level of device performance would be required to meet it. Assume that we desire a link with ,an RF-to-RF gain (GI) of -3 dB over a bandwidth of less than one octave, a noise figure (NF) of 6 dB, and an intermodulation-free dynamic range (IMFDR) of 145 dB in a 1 Hz bandwidth. For the purposes of this discussion we will also limit consideration to amplifierless links using intensity modulation with direct detection (IMDD) and with passive impedance matching at the input and output ends of the link.
{"title":"What Do We Need To Get Great Link Performance?","authors":"C. Cox, E. Ackerman, J. Prince","doi":"10.1109/MWP.1997.740265","DOIUrl":"https://doi.org/10.1109/MWP.1997.740265","url":null,"abstract":"It is well known that the RF performance of optical fiber links falls short of what is desired, and often required. These seem to be the facts of life: links using colmmercially available components have at least 20 dB of RF loss, their noise figures are even greater than their loss, and their dynamic ranges are marginal to acceptable [ 11. Further, all three of these performance parameters degrade significantly with increasing frequency. This sitate of affairs is in stark contrast with the fundamental limits of link performance [2], which have shown that low loss, low noise figure, high linearity links should be possible, even up to fairly high frequencies. So why have we not been able to realize links with such performance? We will pursue the answer to this question by hypothesizing a set of link requirements and seeing what level of device performance would be required to meet it. Assume that we desire a link with ,an RF-to-RF gain (GI) of -3 dB over a bandwidth of less than one octave, a noise figure (NF) of 6 dB, and an intermodulation-free dynamic range (IMFDR) of 145 dB in a 1 Hz bandwidth. For the purposes of this discussion we will also limit consideration to amplifierless links using intensity modulation with direct detection (IMDD) and with passive impedance matching at the input and output ends of the link.","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123867753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"New Optomixer Surpassing Photodetection At Microwaves","authors":"G. Járó, T. Berceli, Attila Hilt, A. Zolomy","doi":"10.1109/MWP.1997.740247","DOIUrl":"https://doi.org/10.1109/MWP.1997.740247","url":null,"abstract":"","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"207 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116283733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It has become increasingly apparent that the next generation of electronically scanned array antennas will require smaller and higher performance signal distribution and time delay beamforming networks. The latter characterisics provides wide instantaneous bandwidth at each steering angle. This eliminates beam squint and enables narrow pulse operation on large antennas, multiple frequency operation and multi-function aperture operation [l , 21. Photonics technology has the potential for having a tremendous impact on the architecture and realization of these systems. Optical interconnects are recognized to provide wider bandwidth, lower loss, smaller size, lighter weight and higher signal isolation than electrical transmission lines. Photonic device and circuit technology can implement modulation and true time delay beamforming functions on the microwave-modulated lightwave signals and provide much wider bandwidth than is presently possible with MMlC technology [3]. In telecommunication applications variable short term memories for queing and packet retiming are needed. In this contribution a noise analysis of true time delay (TTD) optical signal processing systems for arbitrary delay differences is presented. Due to the crosstalk of the switches each stage forms an interferometer which converts the phase noise of the laser source into amplitude noise at the output. This additional noise reduces the signal-to-noise ratio of the system and therefore the phase accuracy of the microwave signal. In wideband beamforming networks consisting of more than 4-5 bit phase shifters the optical true time delay signal processing is carried out in the subgroup level of a phased array antenna. The optical phase shifter shall provide the coarse delay steps ranging from T to n.T (T: period of the microwave signal) while the fine differential delays are provided with electronic delay lines in the transmitheceive modules. Therefore the delay time can be of the order of the coherence time of the laser source. Both the coherent and incoherent region are considered in this contribution.
{"title":"Phase Noise Conversion In Switchable Optical Time Delay Networks For Microwave Signal Processing","authors":"C. Schaffer","doi":"10.1109/MWP.1997.740277","DOIUrl":"https://doi.org/10.1109/MWP.1997.740277","url":null,"abstract":"It has become increasingly apparent that the next generation of electronically scanned array antennas will require smaller and higher performance signal distribution and time delay beamforming networks. The latter characterisics provides wide instantaneous bandwidth at each steering angle. This eliminates beam squint and enables narrow pulse operation on large antennas, multiple frequency operation and multi-function aperture operation [l , 21. Photonics technology has the potential for having a tremendous impact on the architecture and realization of these systems. Optical interconnects are recognized to provide wider bandwidth, lower loss, smaller size, lighter weight and higher signal isolation than electrical transmission lines. Photonic device and circuit technology can implement modulation and true time delay beamforming functions on the microwave-modulated lightwave signals and provide much wider bandwidth than is presently possible with MMlC technology [3]. In telecommunication applications variable short term memories for queing and packet retiming are needed. In this contribution a noise analysis of true time delay (TTD) optical signal processing systems for arbitrary delay differences is presented. Due to the crosstalk of the switches each stage forms an interferometer which converts the phase noise of the laser source into amplitude noise at the output. This additional noise reduces the signal-to-noise ratio of the system and therefore the phase accuracy of the microwave signal. In wideband beamforming networks consisting of more than 4-5 bit phase shifters the optical true time delay signal processing is carried out in the subgroup level of a phased array antenna. The optical phase shifter shall provide the coarse delay steps ranging from T to n.T (T: period of the microwave signal) while the fine differential delays are provided with electronic delay lines in the transmitheceive modules. Therefore the delay time can be of the order of the coherence time of the laser source. Both the coherent and incoherent region are considered in this contribution.","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121882765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Umbach, G. Unterborsch, D. Trommer, G. Mekonnen, R. Braun
A waveguide-integrated photodetector with 0.3 N W responsivity and 70 GHz bandwidth is presented. Millimeter-wave transmission experiments were successfully performed at 64 GHz, demonstrating linear operation up to +10 dBm optical power level. Introduction In view of future cellular broadband communications networks operating in the 60 GHz band and therefore allowing extensive frequency reuse it will be advantageous to distribute the modulated microwave signal via optical fibres to the numerous pico-cells. This system concept allows the remote generation of high quality microwave carriers in the control stations and leads to reduced costs of the base stations in the pico-cellslV2. These base stations will have to be capable of receiving this optical signal and to convert it into a microwave signal, which simply has to be further amplified and fed into an antenna3. For noise considerations an optical power level as high as possible is desired. Therefore, ultrafast photodetectors are required as optic/microwave converters, which provide linear operation up to high input power levels. In the literature several approaches have been reported to realise ultrafast photodetectors. However, in surface illuminated conventional p-i-n photodiodes or metal-semiconductormetal photodetectors4 a high bandwidth entails a limited responsivity. On the other hand, structures with illumination perpendicular to the electric field vector, such as waveguide detectors536 or waveguide integrated photodiodes7 provide high responsivities at ultrahigh frequencies. Furthermore, the uniform distribution of the light absorption over an extended region in these detectors leads to the capability of handling high optical input powers without suffering from carrier induced field screening effects. In this paper the suitability of waveguide integrated p-i-n photodiodes for highly effective conversion of microwave signals in the 60 GHz band at high power levels is demonstrated with respect to application as optic/microwave converters in the base stations of future picocellular communications systems. Detector structure and fabrication The photodetector is formed by a p-i-n diode evanescently coupled to a feeding strip loaded waveguide. The layer stack is grown in a single run by MOVPE on a semi-insulating 1nP:Fe substrate and consists of a 1000 nm thick and a 200 nm thick Ga1nAsP:Fe (Ag= 1.06 pm) waveguide slab and rib layer, respectively, separated by a thin 1nP:Fe etch stop layer. The detector layers start with an n-doped Ga1nAsP:Si (Ag= 1.3 pm) contact layer, followed by an undoped GaInAs absorber layer with a thickness of 400 nm. Selective Zndiffusion in an RTP-furnace is used to form the pn-junction at a depth of about 100 nm. This layer structure was optimised to give a large effective absorption of the evanescently coupled
{"title":"Waveguide-integrated Photodetector For 60 GHz Microwave Transmission at 1.55 /spl mu/gm","authors":"A. Umbach, G. Unterborsch, D. Trommer, G. Mekonnen, R. Braun","doi":"10.1109/MWP.1997.740239","DOIUrl":"https://doi.org/10.1109/MWP.1997.740239","url":null,"abstract":"A waveguide-integrated photodetector with 0.3 N W responsivity and 70 GHz bandwidth is presented. Millimeter-wave transmission experiments were successfully performed at 64 GHz, demonstrating linear operation up to +10 dBm optical power level. Introduction In view of future cellular broadband communications networks operating in the 60 GHz band and therefore allowing extensive frequency reuse it will be advantageous to distribute the modulated microwave signal via optical fibres to the numerous pico-cells. This system concept allows the remote generation of high quality microwave carriers in the control stations and leads to reduced costs of the base stations in the pico-cellslV2. These base stations will have to be capable of receiving this optical signal and to convert it into a microwave signal, which simply has to be further amplified and fed into an antenna3. For noise considerations an optical power level as high as possible is desired. Therefore, ultrafast photodetectors are required as optic/microwave converters, which provide linear operation up to high input power levels. In the literature several approaches have been reported to realise ultrafast photodetectors. However, in surface illuminated conventional p-i-n photodiodes or metal-semiconductormetal photodetectors4 a high bandwidth entails a limited responsivity. On the other hand, structures with illumination perpendicular to the electric field vector, such as waveguide detectors536 or waveguide integrated photodiodes7 provide high responsivities at ultrahigh frequencies. Furthermore, the uniform distribution of the light absorption over an extended region in these detectors leads to the capability of handling high optical input powers without suffering from carrier induced field screening effects. In this paper the suitability of waveguide integrated p-i-n photodiodes for highly effective conversion of microwave signals in the 60 GHz band at high power levels is demonstrated with respect to application as optic/microwave converters in the base stations of future picocellular communications systems. Detector structure and fabrication The photodetector is formed by a p-i-n diode evanescently coupled to a feeding strip loaded waveguide. The layer stack is grown in a single run by MOVPE on a semi-insulating 1nP:Fe substrate and consists of a 1000 nm thick and a 200 nm thick Ga1nAsP:Fe (Ag= 1.06 pm) waveguide slab and rib layer, respectively, separated by a thin 1nP:Fe etch stop layer. The detector layers start with an n-doped Ga1nAsP:Si (Ag= 1.3 pm) contact layer, followed by an undoped GaInAs absorber layer with a thickness of 400 nm. Selective Zndiffusion in an RTP-furnace is used to form the pn-junction at a depth of about 100 nm. This layer structure was optimised to give a large effective absorption of the evanescently coupled","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"114 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132276778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Third-order Intermodulation Distortion And Noise Behavior Of Laser Diode Transmitters Using Optical FM demodulation","authors":"G. Yabre","doi":"10.1109/MWP.1997.740273","DOIUrl":"https://doi.org/10.1109/MWP.1997.740273","url":null,"abstract":"","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130982942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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