The microwave power frequency shifts and light shifts of optically pumped Cs standard at the NRLM(National Research Laboratory of Metrology) were estimated [Ohshima et al.,1991]. Optically pumped Cs standards at the CRL and the NTT (Nippon Telegraph and Telephone Corporation) were constructed using optical feedback and saturated absorption [Maeno et al.,1991; Hisadome et al.,1991].
CRL to develop the atomic fountain frequency standards [Ikegami et al.,1990]. The small-sized hydrogen maser of the CRL was developed with a self-auto tuning system. It employs an enhanced cavity Q method. Its volume is one-eighth of the conventional type [Ohta etal.,1991].
CRL, NAO (National Astronomical Observatory) and NRLM continue routine base GPS time Transfers each other. They weekly report the data to BIPM via GE-Mark 3 to contribute to the Coordinate Universal Time(UTC).
CRL prepared two set of Ku-band communications systems, a microwave time and ranging experiment(MITREX) modem and a prototype modem(I-modem) developed by CRL compatible with MITREX. CRL and KRISS(Korea Research Institutes of Standards and Science) had chanced to use INTELSAT satellites for the two-way time transfer experiment[Imamura et al.,1992, Takahasi et al.,1993].
CRL is developing the two types of ion traps, a Paul trapand a Penning trap. The research in trapping and laser cooling of Ca+ ions in Paul trap and of Be+ ions in a Penning trap was carriedout. Both ions were successfully laser cooled below 1 K. CRL has succeeded in trapping a single ion and observing quantum jumps in the resent experiment on Ca+ ions [Urabe et al.,1992].
The storage time of Yb+ ions trapped in the RF trap was determined by the resonance absorption method in the presence of buffer gas at the NRLM, without and with laser radiation of a frequency equal to the transition from the S1/2 grand state to the P1/2 state [Yoda et al.,1992].
In Japan, there are two main stations for the millisecond pulsar timing observation, one is the Kasima 34 m antenna stationof CRL and the other, the Usuda 64 m antenna station of Space and Astrophysical Science(ISAS). ISAS has been making observation of PSR1937+21 since February 1991 and obtained pulsar timing receiving stability of about 4 x 10-6 t (sec).
Hisadome, K. and M. Kihara, Prototype of an optically pumped cesium beam frequency standard, Proceedings of the 45th Annual Symposium on Frequency Control (1991)
Ikegami, T., S.-I. Ohshima and Y. Nakadan, Laser cooling of Cs atomic beam at the NRLM, Proceedings of the Fifth European Frequency and Time Forum, 190-193 (1991)
Imamura, K., and F. Takahashi, Two-way time transfer via a geostationary satellite, J. Com, Res. Lab., 39-1 (1992)
Maeno, T., H. Saito, J. Umezu, Y. Ohta, M. Kajita and R. Hayashi, Characteristics of a Laser Diode System for an Optically Pumped Cesium Atomic Clock, IEEE Trans, Instrum, Meas., 40-2, 146-148 (1991)
Nakagiri, K., M. Shibuki, N. Kotake and Sebata, Cesium Beam Primary Frequency Standard,Special Issue J.Com,Res.Lab.,39, 23-41 (1991)
Ohshima, S.-I., Y. Nakadan, T. Ikegami and Y. Koga, Light shifts in an optically pumped Cs beam frequency standard, IEEE Trans. Instrum. Meas. 40, 1003-1007 (1991)
Ohta, Y., H. Saito and J. Umezu, Development of a very small hydrogen maser using a loop-gap resonator, Trans. Inst. Electron. Inf. Commun. Eng. C-1 (Japan), J74C-1, 6, 222-230 (1991)
Takahashi, F., K. Imamura, E. Kawai, C. B. Lee, D. D. Lee, N. S. Chung, H. Kunimori, T. Yoshino, T. Otsubo, A. Otsuka & T. Gotoh, Two-way transfer experiment using a INTELSAT satellite in an inclined geostationary orbit, Trans. IEEE Instru. & Meas., 42, (1993)
Urabe, S., et al., Laser cooling of trapped Ca+ and measurement of the 32D5/2 state lifetime, Opt. Lett., 17-16, 1140-1142 (1992)
Yoda, J. and K. Sugiyama, Disappearance of trapped Yb+ ions by irradiation of the resonance radiation, J. Mod. Opt., 39-2, 403-409 (1992)
Dye laser(567nm) was stabilized to the 3P1-1S0 intercombination of 40Ca through the first-derivative signal of the Ramsey fringes detected in a Ca atomic beams. The wavelength of it was compared with an I2-stabilized He-Ne laser and evaluated to be 657.459 439 6 nm(uncertainty 1x10-9)[Ito N, et al., 1991]. On the way of developing the highly stabile dye laser system, spectrum of the dye laser itself was narrowed using a external reference cavity which was stabilized using one of the saturated hyperfine absorption line of the Iodine molecule. The frequency fluctuation of the dye laser reduced to the shot-noise limit and the linewidth of the laser was estimated to be a sub-Hz[Sugiyama K.,et al., 1992]. The performance of the stabilized dye laser was estimated by using two independent Ca atomic beams as a reference and frequency stability of 2x10-12t-1/2(1s< t <100 s) was obtained. Frequency difference between the two Ramsey resonances was within 3kHz over a ten days[Morinaga A. et al.,1993].
1.55mm DFB laser diode was stabilized to vibrational-rotational absorption lines of 12C2H2 and 13C2H2 molecules. Planar lightwave circuit ring resonator and fiber-pigtail-type acoustic optical modulator was used for small laser frequency scanning[Sakai Y., et. al.,1991]. The best frequency stability of within 2 MHz peak-to-peak was achieved and also the dependence of the absorption lines on the temperature and pressure were investigated[Sakai Y. et al.,1992].
An AlGaAs laser diode was frequency stabilized by using a selective reflection spectrum, which had the advantage that a frequency modulation was not required. The system is simple and compact and so can be miniaturized. Rb85-D1 line was used as a reference line and the frequency stability of sy=2.5x10-11(t=60s) was obtained. By using the second derivative of the spectrum, the stability was improved up to s=8x10-12 (t=100s) [Ito T. et al.,1991].
Semiconductor laser has been stabilized to a hyperfine transition frequency of the Rb87-D2(F=2-3) line. With optical feed back, the spectral linewidth was reduced to the 20-times that of the free-running laser. The locking range was 200 MHz and continuous detuning of as large as g/2( half of the natural linewidth of the atomic resonance) was demonstarated[Kozuma M. et al.,1992].
Negative Electrical Feedback was employed to reduce the FM noise of CSP-type AlGaAs semiconductor lasers. A high gain and wideband feedback loop was realized by using a reflection mode of a high finess(25-3500) and stable commercial Fabry-Perot interferometer as a frequency discriminator. FM noise of was reduced lower than the quantum noise level of the free-running laser at 100 Hz< f<4.4 MHz and the spectrum width reduced to 560 Hz[Ohtsu M. et al.,1990].
Optical-electrical double-feedback technique, with high finess (34500 at 830nm) Fabry-Perot cavity, suppressed the FM noise of the CSP-type AlGaAs laser up to 50 dB and narrow line width of up to 7 Hz was obtained. The short term frequency stability of the controlled LD was estimated to sy(t)= 2.4x10-14(t=70 ms)[Shin C. et al.,1990].
Electrical Negative Feedback (NEF) technique was also applied to a Multi-Quantum-Well type DFB laser diode(1.5 mm) and FM noise was reduced to 10Hz2/Hz at 1 kHz<f<10 kHz (f: fourier frequency of the power spectrum) and the spectrum linewidth was narrowed to 250 Hz, the narrowest value for 1.5 mm LD[Kourogi M. et al.,1991].
FM sideband technique was applied, in addition to the NEF, to 1.5 mm three-electrode MQW DFB diode laser to reduce the low AM noise on the frequency error signal from the reflection mode of the high finess optical cavity. Frequency modulation was obtained by the injection current modulating. As a result, the power spectrum of the FM noise reduced to less than 25Hz2/Hz at less than 10 kHz and the Lorentz half spectral linewidth was estimated to be 80 Hz, the narrowest value now which was obtained by NEF method[Nakagawa K.,et al.,1992].
Frequency tracking of a slave semiconductor laser to a highly coherent master semiconductor laser was carried out. By applying the negative electrical feedback to the master laser, the 134 MHz wideband Homodyne Optical Phase-Locke-Loop was realized and 7.5 MHz spectral linewidth free-running semiconductor laser was phase locked to the master laser with a phase error variance of 0.15 rad2[Kourogi M. et al.,1991].
Ito, N., J.Ishikawa, A.Morinaga, Frequency locking a dye laser to the central optical Ramsey friange in a Ca atomic beam and wavelength measurement, J.Opt.Soc.Am,B8,1388-1390(1991).
Ito, T., T.Hashi, T.Yabuzaki, Frequency stabilization of an AlGaAs laser using selective reflection spectrum, Opt.Commun.,82,473-6(1991).
Kourogi, M., et. al.,A 250 Hz Spectral Linewidth 1.5mm MQW-DFB Laser Diode with Negative-Electrical-Feedback, IEEE Photon.Technol.Lett.,3,496-498(1991).
Kourogi, M., et al.,A 134 MHz Bandwidth Homodyne Optical Phase-Locked-Loop of Semi-conductor Laser Diodes,IEEE Phot.Techno.Lett.,3,270-272(1991).
Morinaga, A., N.Ito , J.Ishikawa, K.Sugiyama, T.Kurosu, Accuracy and Stability of a Calcium Ramsey Resonance, IEEE Trans. Instrum and Measu.,42,(1993).
Nakagawa, K.,M.Kourogi ,M.Ohtsu ,Frequency noise reduction of a diode laser by using the FM sideband technique, Opt.Lett.,17,934-936(1992).
Ohtsu, M., M.Murata ,M.Kourogi , FM Noise Reduction and Subkilohertz Linewidth of an AlGaAs Laser by Negative Electrical Feedback, IEEE J.Quantum.Electron.,26,231-241(1990) .
Oonae, A.,T.Kurosawa ,Y.Miki ,E.Sakuma ,Unmodulated CO2 laser stabilized by means of Stark and photoacoustic spectroscopy, Opt. Commun.,88,110-114(1992).
Rhiele, R., A.Morinaga, J.Ishikawa, T.Kurosu, N.Ito, Velocity Selective Absorption by a Long Lifetime Transition in a Ca Atomic Beam, Jpn.J.Appl.Phys.,31,L1542-L1545(1992).
Sakai, Y., I.Yokohama, T.Kominato, S.Sudo, Frequency stabilization of laser diode using a frequency-locked ring resonator to acetylene gas, IEEE Photonics Technol.Lett.,3,868-870 (1991).
Sakai, Y., S.Sudo, T.Ikegami, Frequency stabilization of laser diode using 1.51-1.55 mm absorption lines of 12C2H2 and 13C2H2, J.Quantum Electron.,QE-28,75-81(1992).
Shin, C., M.Ohtsu, Stable semiconductor laser with a 7-Hz linewidth by an optical-electrical double-feedback technique, Opt.Lett.,15,1455-1457(1990).
Sugiyama, K.,A.Morinaga ,Frequency Stabilization of a Dye Laser to a Reference Cavity with Sub-Hertz Relative Linewidth, Jpn. J. Appl. Phys.,30,L1811-L1814(1991).
A 1-m gauge block is measured with an accuracy of 0.15mm using a fringe-counting interferometer[Matsumoto et al.,1991] and a baseline consisting of 7 base points is measured with an accuracy of 30mm using a quasi white lightinterferometer[Seta et al.,1992], and differential hight of oil manometer is measured with an accuracy of 0.26 mm using a heterodyne interferometer[Ueki et al.,1992]. An angular shearing interferometer for collimation in the nanoradian range is developed by Tanaka et al., 1990].
The diameter of a single-crystal silicon sphere is determined with a standard deviation of 8.6 nm using a multi-wavelength interferometer[Fujii et al.,1992] and the thermal expansions of pure water are measured within an accuracy of 1x10-6 in the range of 0 to 85 C[Takenaka et al., 1990] and within an accuracy of 0.2 to 0.5 ppm in the range of 0 to 44 C [Watanabe,1991].
An absolute linewidth measuring system is developed, based on a scanning electron microscope and a laser interferometer[Hatsuzawa et al., 1990]. A high-precision interferometric dilatometer has been developed for use in the evaluation of low-expansion materials[Aikawa et al., 1990] and intercomparison of interferometric dilatometers is achieved at NRLM and NPL[Okaji et al., 1991].
Edlen's equation for determining the refractive index of air was studied in the temperature range of 20 C to 60 C[Shimizu et al., 1992]. The refractive indices of air along the optical path of a system were measured at real time within an accuracy of 0.13 ppm in the distance range of about 18 km bya light-modulation technique [Fujima et al.,1992], with an accuracy of 0.15 ppm in the range of about 235 m, interferometrically,[Matsumoto et al.,1992] and with an accuracy of 2x10-7 in the range of 50 cm using a laser-diode-pumped YAGlaser and its second-harmonic wave [Matsumoto et al.,1992]. The refractive index of optical glasses are interferometrically measured within an accuracy of 1x10-6[Seino et al., 1990].
Aikawa, H., Masahiro Okaji, Hidetaka Imai, Development of a precision dilatometer by means of optical heterodyne interferometry, Transac.Soc.Instrum. Control. Eng., 29, 1131-1138(1990)
Fujii, K., Mitsuru Tanaka, Yoshiaki Nezu, Kan Nakayama, Ryouhei Masui, Interferometric measurements of the diameters of a single-crystals silicon sphere, Rev. Sci. Instrum., 63, 5320-5325(1992)
Fujima, I., Hirokazu Matsumoto, Katuo Seta, Tadanao O'ishi, Two-color Correction for the Atmospheric Refractive Index in Long Distance Measurement, KOUGAKU, 21, 871-877(1992)
Hatsuzawa, T., Kouji Toyoda, Yoshihisa Tanimura, A metrological electron microscope system for microfeatures of very large scale integrated circuits, Rev. Sci.Instrum., 61, 975-979(1990)
Matsumoto, H., Tokuyuki Honda, High-accuracy length-measuring interfero-meter using the two-colour method of compensating for the refractive index of air, Meas. Sci. Technol., 3, 1084-1086(1992)
Matsumoto, H., Yucong Zhu, Shigeo Iwasaki, Tadanao O'ishi, Measurement of the changes in air refractive index and distance by means of a two-color interferometer, Appl. Opt., 31, 4522-4526(1992)
Okaji, M., K.P.Birch, Intercomparison of Interferometric Dilatometers at NRLM and NPL, metrologia, 28, 27-32(1991)
Saitoh, M., Hirokazu Matsumoto, Ichirou Fujima, Tadanao O'ishi, High-Resolution Distance-Meter Using Optical Wave-Guide Modulators, KOUGAKU, 22, 142-145(1993).
Seino, S., Masahiko Daimon, Interferometric Measurement of Refractive indices of Optical Glasses, KOUGAKU, 19, 249-251(1990)
Seta, K., Shigeo Iwasaki, B.K.Ward, Tadanao O'ishi, Establishment of a High Accuracy Baseline for EDM Calibration in the NRLM Tunnel, J. Geodetic Soc. of Japan, 38, 151-162(1992)
Shimizu, Y., Yoshiaki Akimoto, Yoshihisa Tanimura, Hirokazu Matsumoto, Akito Okamoto, Experimental Study on Edlen's Equation in the Temperature Range from 20 C to 60 C, Rev.Laser Eng.,20, 146-151(1992)
Takenaka, M., Ryouichi Masui, Meaurement of the Thermal Expansion of Pure Water in the Temperature Range 0-85 C, metrologia, 27, 165-171(1990)
Tanaka, M., Kan Nakayama, A New Angular Shearing Interferometer for Collimation in the Nanoradian Range, Jpn.J.Appl.Phys., 29, 427-433(1990)
Toda, H., Masamitsu Haruna, Hiroshi Nishihara, Integrated-Optic Heterodyne Interferometer for Displacement Measurement, J.Lightwave Technol., 9, 683-687(1991)
Ueki, M., Akira Ooiwa, Precise Measurement of Differential Hight of Oil Manometer by means of Heterodyne Interferometer, J.Jpn. Soc. Prec. Eng., 58, 120-126(1992)
Watanabe, H., Thermal Di;atation of Water between 0 C and 44 C, metrologia, 28, 33-43(1991)
An automated voltage divider of 10 to 1 was developed [Endo et al., 1991] and an automated system composed of a combination of the JJAVS system and the divider has been developed to calibrate a 10-V output of the Zener diode-based reference standard (ZDRS) [Sakamoto et al., 1992].
A comparison among three sets of similar 1-V automated JJAVS systems was carried out to confirm that each system can be operated with the assigned uncertainty of about 1x10-8 for daily calibration work of ZDRSs [Iwasa et al., 1992].
A comparison of JJAVS systems was internationally performed between the BIPM (Bureau International des Poids et Mesures) and the ETL to investigate the ultimate accuracy of the JJAVS which should be in about 10-10 [Reymann et al., 1993].
A resistance calibration system based on the quantum Hall effect has been used to maintain the primary resistance standard at the ETL adopting RK-90 ( the conventional value of the von Klitzing constant) since January 1990 [Kinoshita et al., 1991].
In the course of investigating a sample dependence of the quantum Hall effect, anomalously offset quantized Hall plateaus has been observed in Si-MOSFETs with high mobility [Van Degrift et al., 1992]
An automated comparison system of ac-dc thermal converters has been developed to reduce the measurement uncertainty to less than 1 ppm by using the two-DVM method and differential method [Sasaki et al., 1992], [Takahashi et al., 1992].
Endo T., Y. Sakamoto, T. Sakuraba, Y. Murayama, H. Yoshida and S. Odawara, Automated voltage divider to calibrate a 10-V output of Zener voltage standard, IEEE Trans. Instrum & Meas., 40, 333-336 (1991)
Iwasa A., Y. Sakamoto, H. Yoshida and T. Endo, Mutual comparisons of fully automated Josephson-junction-array-voltage-standard systems, CPEM'92 Digest, 369-370 (1992), and to be published in IEEE Trans. Instrum. & Meas. (1993)
Kinoshita J., N. Nishinaka, K. Segawa, C. T. Van Degrift and T.Endo, Measurements of the quantized Hall resistance at ETL, IEEE Trans, Instrum & Meas., 40, 249-252 (1991)
Reymann D., A. Iwasa, H. Yoshida, T. Endo and T. J. Witt, Comparison of Josephson voltage standards of the Electrotechnical Laboratory and the Bureau International des Poids et Mesures, Metrologia, 29, 389-395 (1992)
Sakamoto Y., A. Odawara and T. Endo, Computer-controlled low thermal emf rotary switch, IEEE Trans. Instrum. & Meas., 40, 337-339 (1991)
Sakamoto, Y., H. Yoshida, T. Sakuraba, S. Odawara, Y. Murayama and T. Endo, Josephson junction array voltage standard at ETL, IEEE Trans. Instrum. & Meas., 40, 249-252 (1991)
Sakamoto. Y, T Endo, and T. Sakuraba, A 10-V measuring system using an automated voltage divider and a 1-V Josephson array, CPEM'92 Digest, 302-303 (1992), and to be published in TEEE Trans. Instrum & Meas. (1993)
Sasaki H., K. Takahashi and T. Endo, Automated measurement system for thermal ac-dc transfer standards, CPEM'92 Digest, 58-59 (1992), and to be published in IEEE Trans. Instrum. & Meas. (1993)
Takahashi K., H. Sasaki and T. Endo, An ac voltmeter calibration system by a differential and a two-DVM method, CPEM'92 Digest, 72-73 (1992), and to be published in IEEE Trans.Instrum. & Meas. (1993)
Van Degrift C. T., K. Yoshihiro, M. E. Cage, D. Yu, S. Segawa, J. Kinoshita and T. Endo, Anomalously offset quantized Hall plateaus in high-mobility Si-MOSFETs, Surface Science 263, 116-119 (1992)
Yoshida H., Y. Sakamoto, and T. Endo, Circuit precaution for stable operation of Josephson array voltage standard, IEEE Trans. Instrum & Meas., 40, 305-308 ( 1991)
A small and very wide-band dipole antenna using FET's with a bandwidth exceeding 200Hz to 1000MHz was developed. The antenna factor in free space was measured by using a TEM cell and the standard antenna method with error of 3.2% [Matsui, 1991]. A field strength standard for 100-1000MHz using broadband short dipole antennas was developed. The uncertainty of the standard is within 1.6% [Matsui, 1991].
A highly sensitive electric field sensor was developed using a LiNbO3 optical modulator. The minimum detection level of 1mV/m and bandwidth of 1GHz are obtained[Tajima et al., 1991]. The characteristics of the above electric field sensor were analyzed. The sensor was used to measure an electromagnetic impulse with peak value larger than 10V/m and width wider than 5ns[Kuwabara et al., 1992]. The recent progress in fiber optic antennas for EMC measurement that has been made in Japan is summarized[Tokuda et al., 1992].
The normalized site attenuation is theoretically analyzed and its applicability is discussed. It revealed that the correction factors in ANSI standard are inappropriate and that different correction factors should be investigated[Sugiura, 1990]. New correction factors for the normalized site attenuation are proposed for various measurement configurations at 3-, 10-, and 30-m test sites[Sugiura et al., 1992].
Superresolution techniques for time-domain measurements with a network analyzer was proposed using a multiple signal classification algorithm which enhances the accuracy of measurement for narrow-band devices such as antenna[Yamada et al., 1991]
Kawana, T., M. Osakabe, and K. Koike, Evaluation of dipole antenna balun loss in the UHF band, IEEE Trans., IM-40 480-482(1991)
Kuwabara, N., K. Tajima, R. Kobayashi, and F. Amemiya, Development and analysis of electric field sensor using LiNbO3 optical modulator, IEEE Trans., EMC-34, 391-396(1992)
Matsui, T., A wide-band FET antenna and its calibration, IEEE Trans., IM-40 47-49(1991)
Matsui, T., A 100-1000MHz field strength standard for an anechoic chamber, IEEE Trans., IM-40 736-741(1991)
Sugiura, A., Formulation of normalized site attenuation in terms of antenna impedances, IEEE Trans., EMC-32 257-263(1990)
Sugiura, A., T. Shinozuka, and A. Nishikata, Correction factors for normalized site attenuation, IEEE Trans., EMC-34-461-470(1992)
Tajima, K., N. Kuwabara, and F. Amemiya, Highly sensitive electric field sensor using LiNbO3 optical modulator, IEICE Japan E74, 1941-1943(1991)
Tokuda, M., and N. Kuwabara, Recent progress in fiber optic antennas for EMC measurement, IEICE Japan E75-B, 107-114(1992)
Yamada, H., M. Ohmiya, Y. Ogawa, and K. Itoh, Superresolution techniques for time-domain measurements with a network analyzer, IEEE Trans., AP-39, 177-183(1991)
A step attenuator was developed for use in multimode fiber-optic systems with an incoherent light source at 850 nm. This attenuator represented an improvement in spectrum dependency. The evaluated uncertainty of the system for calibrating the attenuation was +-0.02 dB / 10 dB (+-2s) for attenuations of 20 - 50 dB [Iwasaki et al., 1989]. The result of the international intercomparison of incremental attenuation steps of the fiber optics attenuator was reported. The maximum difference among the mean values of the measurements at ETL, Japan, CSELT, Italy, VSL, Netherlands, PTB, Germany and LCIE, France were less than 0.03 dB / 10 dB [Iwasaki et al., 1991].
An universal calibration method for four-terminal-pair (4TP) admittance standards was developed for frequencies up to 10 MHz. Implementation of the method required only a set of driving-point-impedance measurements using proven one-port technology, and calculation of 4TP transfer admittance and output impedances using an impedance matrix (Z-matrix) [Suzuki, 1991]. A measurement technique of HF - VHF impedance by detecting voltage and current was proposed. Theoretical and experimental analyses suggested that the accuracy can be better than the vector reflectmetry [Yokoshima, 1992].
Inoue,T. and K. Yamamura, Development of fiber-optic power standard in ETL, Densi Tokyo, (published by IEEE Tokyo Section), No.28, 136-139 (1989)
Iwasaki,T. and I.Yokoshima, Calibration of a step attenuator for multimode fiber optics, IEEE Trans.Instrum. Meas., 38, 2, 591-594 (1989)
Iwasaki,T.,B.Sordo, J.de Vreede, W.Moller and Y.Bettinelli, International intercomparison of attenuation in fiber optic systems: Multimode fiber and LED-based Comparison, IEEE Trans.Instrum.Meas., 40, 5, 855-859 (1989)
Suzuki,K., A new universal calibration method for four-terminal-pair admittance standards, IEEE Trans. Instrum. Meas., 40, 2, 420-422 (1991)
Suzuki,Y., A.Murata, M.Araragi and T.Inoue, Calorimeter with compensative absorber for measuring microwatt level optical power, IEEE Trans.Instrum.Meas., 40, 2, 219-221 (1991)
Yokoshima,I., RF impedance measurements by voltage-current detection, Technical Digest of CPEM'92 at Paris, 248-249 (1992)
Optical time-domain reflectometer (OTDR) can be widely applied to the optical device measurements. Strain distributions along optical fibers in a 1.3-km-long cable before and after installation were measured using Brillouin optical-fiber time domain analysis [Tateda et al., 1990]. The residual strains in the installed optical fibers were found to vary from zero to 0.07 % depending on the conduit configuration and installation procedure. A measuring method for optical fiber attenuation, BOTDA (Brillouin optical-fiber time-domain analysis) was proposed [Horiguchi et al., 1989]. Dynamic range was theoretically confirmed to be 10 dB greater than that of the conventional OTDR. An interferometric OTDR system with high spatial resolution was developed for diagnosis of optical waveguides and hybrid opical circuits [Takada et al., 1990]. Spatial resolution as short as 14 mm and minimum detectable reflectivity of -100 dB were achieved at 1.3-mm wavelength.
Signal polarization critically affects the transmission characteristic of a single-mode fiber. Real-time polarization fluctuations measurements in an optical fiber submarine cable during laying and recovery in a 6000 m deep-sea trial was investigated [Namihira et al., 1989]. The maximum power spectra of the polarization fluctuations were found experimantally less than about 50 Hz. A polarimetric optical fiber sensor using a Frequency stabilized semiconductor laser was reported [Tsuchida et al., 1989]. The minimum detectable temperature change was experimentally evaluated to be less than 0.005 C.
Narrow-linewidth signal is important for coherent optical transmission as well as for optical sensing. A simple interferometric method for monitoring mode hopping in tunable external-cavity semiconductor lasers was proposed, in which a fiber Mach-Zehnder interferometer is used [Ohtsu et al., 1989]. The method was applied to monitoring and controlling a laser frequency. A reflection-type delayed self-homodyne/heterodyne method for optical linewidth measurements was proposed [Iiyama et al., 1991]. The optical configuration is simple and the beat signal has a resolution twice that of the conventional method.
Fluoride glasses have potential for ultra-low-loss optical fibers. Temperature dependence of refractive index dispersion and material dispersion of fluoride glasses was measured [Mitachi, 1989]. The measurements indicated that fluoride glasses can compensate for such dependence existing in silica glasses and fibers.
Horiguchi, T. and M. Tateda, BOTDA-Nondestructive Measurement of Single-Mode Optical Fiber Attenuation Characteristics Using Brillouin Interaction: Theory, IEEE J. of Light. Tech.,7, 8, 1171-1176 (1989)
Iiyama, K., K. Hayashi, Y. Ida, H. Ikeda, and Y. Sakai, Reflection-Type Delayed Self-Homodyne Method for Optical Linewidth Measurements, IEEE J. of Light. Tech.,9, 5, 635-640 (1991)
Kawanishi, S., A. Takada, and M. Saruwatari, Wide-Band Frequency-Responce Measurement of Optical Receivers Using Optical Heterodyne Detection, IEEE J. of Light. Tech.,7, 1, 92-98 (1989)
Mitachi, S., Dispersion Measurement on Fluoride Glasses and Fibers, IEEE J. of Light. Tech.,7, 8, 1256-1263 (1989)
Namihira, Y. and H. Wakabayashi, Real-Time Measurements of Poralization Fluctuations in an Optical Fiber Submarine Cable in a Deep-Sea Trial Using Electrooptic LiNbO3 Device, IEEE J. of Light. Tech.,7, 8, 1201-1206 (1989)
Ohtsu, M., K.-Y. Liou, E. C. Burrows, C.A. Burrus, and G. Eisenstein, A Simple Interferometric Method for Monitoring Mode Hopping in Tunable External-Cavity Semiconductor Lasers, IEEE J. of Light. Tech.,7, 1, 68-76 (1989)
Takada, K., N. Takato, J. Noda, and N. Uchida, Interferometric optical-time-domain reflectometer to determine backscattering characterization of silica-based glass waveguides, J. Opt. Soc. Am. A,7, 5, 857-867 (1990)
Takara,H., S. Kawanishi, Y. Yamabayashi, and M. Saruwatari, Ultra High-Speed Optical Waveform Measurement Method Using Optical Sampling with Sum-Frequency Generation, Trans. IEICE, J75-B-I, 5, 372-380 (1992)
Tateda, M., T. Horiguchi, T. Kurashima, and K. Ishihara, First Measurement of Strain Distribution Along Field-Installed Optical Fibers Using Brillouin Spectroscopy, IEEE J. of Light. Tech.,8, 9, 1269-1272 (1990)
Tsuchida, H., Y. Mitsuhashi, and S. Ishihara, Polarimetric Optical Fiber Sensor Using a Frequency Stabilized Semiconductor Laser, IEEE J. of Light. Tech.,7, 5, 799-803 (1989)
In land mobile communications, digital cellular system, personal communication system, and mobile packet communication system have been very actively studied. Especially, in personal communication system, new system concept developed from cordless telephone system [Hattori et al., 1990] and from digital cellular system[Nakajima et al., 1992] are proposed. Papers concerning with antenna & propagation are adaptive antenna [Kohno, 1991] and 2GHz microcellular propagation[Nagata, 1991]. In voice coding, evaluation system[Miki et al., 1991] is investigated.
In satellite communications, the engineering test satellite ETS-VI has been developed to pursue experimental missions of multi-beam satellite communications covering Japan with 13/5 beams and is waiting for launch by Japan's first 2-ton class rocket H-2. The ETS-VI employs advanced onboard equipment [Tanaka et al,1992] including deployable 3.5- and 2.5-meter reflector antennas [Ohtomo et al, 1990], 30-GHz band full-MMIC ultra lightweight transponder [Kato et al, 1990], 2.5GHz-band multi-port transponder [Horikawa et al, 1992].
Hattori, T., Sekiguchi, H., Kohiyama, K. and Yamamoto, H., Personal Communication -Concept and Architecture, IEEE ICC'90, 335.4 . (1990)
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Miki, T. and Suda, H., Evaluation system for mobile radio speech codec , IEEE Vehicular Technology Conference, St. Louis, U.S.A., 657-662(1991)
Murase, T., Hashimoto, A. and Segawa, J, Design and Performance of the SDH based Microwave Digital Radio Systems, 3rd ECRR, 48-55 (1991)
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Ohtomo, I., Kumazawa, H.,.Kawakami, Y. and Yasaka:, T., Development of the on-board fixed and mobile multi-beam antenna for ETS-VI satellite , 13th ICSSC, 90-0805 (1990)
Tanaka, M., Yamamoto, K. and Horikawa, K., Ka-band and S-band transponder technologies for satellite on-board multibeam communication system, 4th Asia Pacific Microwave Conference Proceedings , APMC '92, 1, 261-264 (1992)
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