An optical time domain reflectometer for single-mode fibers has been designed and constructed at a 1.3 µm wavelength. A fast digital averager enables 44 dB signal-to-noise ratio improvement within about 40 seconds. Curve fitting by a least squares method reduces the variation in fiber loss measurements. By using an acoustooptical directional coupler, Fresnel reflection is removed. In addition, backscattered signal fluctuation caused by polarization fluctuation is suppressed to a negligible extent. Current drift in receiving circuits is decreased by using a drift compensation circuit. The optical time domain reflectometer that has been built can locate breaks in single-mode fibers with attenuations as high as 17.5 dB.

High-speed power line communication (PLC) can transmit an information signal of several hundred megabits per second over the power lines that transport electrical energy. Because this system employs unmodified existing transmission lines and the signal can be accessed through the simple interface of an ordinary electrical outlet, it promises to serve as the most effective transmission system for supporting information home appliances. For high-speed PLC to become practical requires that the frequencies used be expanded to 30 MHz, a frequency band is already used by many wireless communication systems. Thus, shared use with those systems is the most important problem. This paper introduces technical trends related to that issue.

It has become very important to study the lightning surges that were induced in subscriber telecommunication equipment because of the increase of susceptible circuits to the over voltage. The test generator is desire to be developed evaluating the resistibility of equipments against lightning surges. This paper proposes a new lightning-test method for subscriber telecommunication equipment. The waveform of the test generator simulates that of the induced lightning surge voltage caused by a nearby return stroke. The output impedance of the surge generator is determined to match the common-mode impedance of telecommunication lines. The damaged condition of circuit parts and the trouble occurrence rate estimated by using this method agree well with actual observations.

The possibility of applying a recently proposed emission source location method, which is based on CISPR measurements, to sources with arbitrary directional current components is studied. We propose a new finding algorithm in which the horizontal and the vertical current components are estimated at the same time by taking into account the contribution of horizontal current components when calculating the vertical electric field. As a result of experimental verification by using two spherical dipole antennas as ideal emission sources, estimated values show good agreement with the original ones in the frequency range from 300 MHz to 1 GHz, where the position estimation deviation d was less than 0.15 m, the amplitude estimation deviation j was less than 2.1 dB, and furthermore the angle of current direction could be estimated. Consequently, this method with the presented new algorithm can be applied to find radiated emission sources even when the current components point to arbitrary directions.

For common-mode noise current reduction, a CMC (Common Mode Choke) is widely used in signal transmission line circuits consisting of a ground and two conductors (a balanced transmission line). However, a common-mode noise current reduction characteristic is not clearly analyzed yet in the case that a CMC is inserted in a balanced transmission line. In this paper we propose the calculation method of CMC insertion losses and derive an equation to analyze the common-mode current characteristics of a balanced transmission line with a CMC inserted. The analyzed frequency range is from 100 kHz to 100 MHz. We conclude that in the frequency range up to 30 MHz: (1) the proposed insertion loss calculation method is useful for analyzing CMC insertion losses in differential-mode and in common-mode; (2) the derived circuit equation can be applied for analyzing the common-mode current characteristics of a balanced transmission line locally unbalanced with conditions of a CMC inserted; (3) the proposed calculation method may give the expected results that a CMC should be placed in a signal source side of an unbalanced point of a pair-cable for reduction of common-mode currents; and (4) if it is placed in a terminal (or load) side of an unbalanced point, there is no effect, or rather common-mode currents are increased by the insertion of a CMC.

This paper describes measurements of fiber loss and splice loss by backward Rayleigh scattering in fibers. Fiber loss measuring accuracy less than0.04 dB is obtained, and the repeatability is very good in comparison with conventional cut-back method. For splice loss measurement, the measuring accuracy is the same as the above. It is found that the splice loss measured by the backscatter method is different from the true value for fibers with different Rayleigh-scattering losses. To obtain the true value, several correction method for the measured value are proposed. Application of the backscatter method to fault location reveals that even an 8.6 km distant fiber end-face without Fresnel reflection can be discriminated.

Polarization mode properties of a polarization-preserving fiber having elliptical stress-cladding with barrier layer around the core are clarified theoretically and experimentally. Normalized frequency dependence of modal birefringence and polarization mode dispersion were measured for the polarization-preserving fiber. It is found from theoretically and experimentally evaluated results that the elliptical stress-cladding fiber has polarization-mode properties similar to those of the polarization-preserving fiber having isolated stress-producing lobes. Stress profiles of the elliptical stress-cladding fiber were measured and calculated for confirming the polarization-mode properties of the fiber. It is known from the measured results that the similarities of polarization-mode properties between the elliptical stress-cladding fiber and the fiber will stress-producing lobes are caused by those of differential stress profiles around the core regions between them.

An electric filed sensor using Mach-Zehnder interferometers has been designed to operate more than 10 GHz. The velocity of optical wave on the waveguide is investigated to determine the electrode length, and the characteristics of frequency response are analyzed using the moment method to determine the sensor element length. The electrode length of 1 mm and the element length of 8 mm are settled by these investigations. An isotropic electric field sensor is constructed using three sensors. The minimum detectable electric field strength is 22 mV/m at frequency bandwidth of 100 Hz. This is about 100 times for the conventional electric field sensor using the similar element. The sensitivity deviation is within 3 dB when temperature changes from 0 degree to 40 degree. The deviation of directivity can be tuned within 1 dB to calibrate the sensitivity of the each element. The sensitivity degradation is within 6 dB up to 5 GHz and within 10 dB up to 10 GHz. This is almost agree with the calculated results. The sensor can measure almost the same waveform as the applied electric field pulse whose width is 6 ns and rise time is less than 2.5 ns.

Far-end measurement instrument for baseband frequency response, based on swept frequency method, is designed and constructed. In constituting the measurement instrument, it is important to stabilize modulation frequency characteristics of laser diode which is significantly affected by externally reflected light to the laser diode. It has been found that by coupling laser diode to a fiber with obliquely polished end face, the influence of externally reflected light can be negligibly small. Optimum coupling conditions, concerning tilt angle of fiber end and distance between fiber and laser facet are clarified. Moreover, automatic power control and temperature control circuit has been applied to the above laser to fiber coupler and far-end measurement instrument of baseband frequency response has been constructed. As a result, sufficient stabilization of modulation frequency characteristics to measure baseband frequency response of graded-index optical fiber has been attained.

We have studied on the interference test method from IEEE802.11b to IEEE802.11g as an interference source with wide band spectrum by using the opened PW cell, and it is clear that the throughput of IEEE802.11g for only IEEE802.11b Ch.4 signal wave as the interference wave, whose frequency spectrum is almost not overlapping with IEEE802.11g, is almost not interfered by IEEE802.11b, but the throughputs for all other channels from Ch.5 to Ch.8 as the interference wave are interfered and decrease to below 2 Mbps. By comparing with conventional radiated RF electromagnetic field immunity test specified by IEC 61000-4-3, it is clear that the conventional immunity test cannot simulate the interference phenomena from IEEE802.11b to IEEE802.11g. Next, we tried to perform the interference test of the Bluetooth against the wireless LAN IEEE 802.11b as a disturbance source. As a result, it is revealed that the throughput of Bluetooth decreases according to increasing the interference wave level, and communication between EUT (slave) and the master of Bluetooth is interrupted for the interference wave corresponding to Ch.7 (244210 MHz). However, in the conventional immunity test specified by IEC 61000-4-3, the throughput of the Bluetooth does not affect for the all disturbance waves corresponding to the center frequency of bandwidth on the cannel of IEEE802.11b. Therefore, it is needed for the wireless LAN and the Bluetooth to develop new radiated immunity test method, which has the disturbance wave with wide bandwidth.

Relating to the radiated emission sources finding method based on CISPR emission measurement system, which uses only amplitude data without phase data, the applicability to horizontally polarized sources was studied. We experimentally verified by using two spherical dipole antennas as ideal emission sources in the frequency range from 300 MHz to 1GHz. As the results, the position estimation deviation Δd was less than 0.09 m, the amplitude estimation deviation Δj was less than 1.5 dB, in which position estimation accuracy was raised so much compared with that for vertically polarized sources, and additionally the angle of its horizontal current direction could be estimated. Furthermore, it was revealed that this method can be also applied even when several sources exist, consequently the applicability of this method has been greatly expanded.

Recent progress in electromagnetic compatibility (EMC) technology has created a need for small and wideband antennas that can be used to measure the quality of EMC measurement facilities and to measure electric field strength for immunity tests and human hazard studies. Antennas using fiber optics are being developed because this kind of antenna has the wideband property and can eliminate the influence of the coaxial cable. This paper first summarizes the development of fiber optic antennas for EMC measurement and the construction of practical fiber optic antennas. It then describes the recent progress that has been made in Japan. This progress includes the electromagnetic source and the electric field sensor using a spherical dipole antenna with O/E or E/O converters, and it includes a wideband electric field sensor using electro-optical crystals.

The design method for sensitivity and frequency response of an electric field sensor using a Mach-Zehnder interferometer (an optical E-field sensor) has been developed in order to measure electromagnetic environments and the performance of measuring facilities. The designs of the optical modulator, sensor elements, and sensitivity were analyzed theoretically by using an accurate equivalent circuit of the sensor. Then an actual sensor was fabricated, and its characteristics of the sensor were evaluated experimentally. The results show that the designed sensitivity and frequency response were optimal. The optical output deviation when the temperature increased from 0 to 40 was reduced to within 2 dB. The minimum detectable electric field strength was 17 dBµV/m (8 µV/m), and the dynamic range was more than 100 dB. The frequency response of the sensitivity was almost flat between 200 Hz and 900 MHz.

Based on the test method proposed by Sub-Committee G of the International Special Committee on Radio Interference, most telephone receivers in Japan have insufficient immunity to acoustic noise caused by radio-frequency fields. This is because the modulation depth of the RF signal used is too high to accurately simulate the audio-frequency components of TV video signals. Reducing the modulation depth from 80% to 5% produces a more realistic simulation.

In this paper, a balance-unbalance conversion factor (TCTL: Transverse Conversion Transfer Loss, TCL: Transverse Conversion Loss) and a radiated emission for differential type microstrip lines with a partial unbalance on a PCB (Printed Circuit Board) are investigated. As the result, after inserting an unbalance element, it can be seen that a radiated emission increased according to the deterioration of TCL. The calculated results of the TCTL and TCL by using 4-terminal pair network chain matrix agreed with the measured results very well. In order to calculate radiated emission from the differential type microstrip lines, a common mode current on differential type microstrip lines with a partial unbalance was calculated by using 4-terminal pair network chain matrix. The calculated results of the radiated emission also agreed with the measured results.

Simple formula has been proposed to estimate baseband bandwidth of an optical transmission line made of different fibers spliced together. Using the formula, cumulative bandwidth is predicted merely from the bandwidth for each individual fiber. The usefulness of the formula has been confirmed by experiments.

We study radiated RF (radio-frequency) electromagnetic field immunity test system for wireless LAN system by using opened PW (Parallel Wired) cell, in which metal cover is removed. Leakage electric field at distance of 160 cm from the opened PW cell decreases until 30 dB, and then does not affect to operation of the AP (Access Point) composed of the wireless LAN system that communicates EUT (Equipment Under Test) installed in the PW cell. NSA (Normalized Site Attenuation) between EUT and AP changes only several dB by inserting the PW cell, and then it can be concluded that the effect of PW cell for radio wave property of wireless communication system is negligible small. In addition, we try to measure dependencies of impressing level of disturbance wave on a throughput of wireless LAN systems IEEE802.11b and IEEE802.11g. As a result, it is confirmed that the radiated RF electromagnetic field immunity test system for wireless LAN system can be composed by using the opened PW cell without affecting from impressing disturbance wave.

A multiple fiber connector with an alignment hole for a multiple extrusion unit is proposed. An average connector loss of 0.27 dB is achieved by employing index matching oil. Furthermore, the cause of the loss is evaluated, and it is shown that the calculated losses agree with the experimental values.