The effectiveness and possible applications of all-optical signal processing using highly-nonlinear dispersion-shifted fibers (HNL-DSFs) are described. Transparent and simultaneous processings of multi-channels WDM signal are key features of optical fiber processors. Simultaneous wavelength conversion of 3210 Gb/s WDM signal by four-wave mixing, all-optical 3R regeneration of 220 Gb/s WDM signal using nonlinear loop mirrors, and simultaneous recovery of 2020 GHz WDM optical clocks by supercontinuum were successfully demonstrated using HNL-DSFs, and possible applications of ultra-fast and multi-channel processing in future photonic networks are discussed.

A photonic crystal fibre has an array of microscopic air holes running along its length. The periodicity of the array is broken by a deliberate "defect" that acts as a waveguide core. Light is confined to this core by the holes. Although some designs of photonic crystal fibre guide light by total internal reflection and so can be considered analogues of conventional optical fibres, their properties can be strikingly different. Other designs guide light by photonic bandgap confinement and represent a totally new type of fibre.

A photonic crystal fibre has an array of microscopic air holes running along its length. The periodicity of the array is broken by a deliberate "defect" that acts as a waveguide core. Light is confined to this core by the holes. Although some designs of photonic crystal fibre guide light by total internal reflection and so can be considered analogues of conventional optical fibres, their properties can be strikingly different. Other designs guide light by photonic bandgap confinement and represent a totally new type of fibre.

This paper describes the evaluation of a fiber-optic reflective displacement sensor that is compensated for variations in light source intensity, pressure, temperature and opacity of ambient medium. Additionally, the distance information is averaged over several points on the target surface, which reduces signal fluctuations due to inhomogeneities. Furthermore, a practical optical fiber reflective sensor model of measuring oil film thickness for thrust bearing is set up in this paper. Actual measurements were made with HEC 3000 tons' thrust bearing and the results were in good agreement with theoretical calculations.

The power coupling coefficients between cores of waveguide systems with random geometrical imperfections along the fiber axis are determined by comparing numerical solutions of the coupled mode equations with numerical solutions of the coupled power equations and the dependence of the power coupling coefficient on the correlation length with respect to the propagation constants of modes is clarified. When the correlation length D is small the power coupling coefficient is proportional to κ 2 D where κ is the mean mode coupling coefficient and is independent of the fluctuation of the propagation constants. For sufficiently large D the power coupling coefficient dc decreases in proportion to D-1 with increasing D and when D , dc 0. Then the dependence of the power coupling coefficient on the mode coupling coefficient and the fluctuation of the propagation constants δ β is expressed as a function of a single variable κ /δ β .

IOG is a link layer protocol specifically designed for the high speed and bandwidth efficient transmission of IPv4 and IPv6 datagrams over optical fibers. That is, IOG is a simple point-to-point packetization protocol over a bit stream with a low bit error rate. MTU of IOG is 1535, which is long enough for the Internet with IPv6 multicast packets and Ethernet frames. IOG has a framing structure of fixed length (2048 bytes) for synchronization, CRCC (Cyclic Redundancy Check Code) and scrambling. A frame consists of 4 bytes of a frame header, 2040 bytes of a frame payload and 4 bytes of a frame trailer for CRCC. CRCC is also used for scrambling. A frame header consists of a 21 bit flag sequence ("011111111111111111110") and a 11 bit packet boundary pointer. A packet has an 11 bit length field and a 21 bit label field. The label field contains an Ethertype or a link layer label. Packets are packed continuously in frame payload. A packet is at least 20 and at most 1535 bytes long. If there are no packets to send, 20 byte packets of Ethertype 0 are sent, which is ignored by the receiver. A packet may be included in two adjacent frames. The packet boundary pointer in a frame header of a frame points to the first packet boundary of the frame, which means that once a frame synchronization is established, packet synchronization is also established. IOG is designed to allow high-speed implementations to enable 32 or 64 bit parallel processing. CRC polynomial of X32 + X2 + X + 1 is newly designed for high-speed 32 or 64 bit parallel calculation and frame wise SECDED (Single Error Correction, Double Error Detection). IOG is applicable to long haul transmission of IP datagrams in Internet backbone and to inter-chip or inter-module transmission of IP datagrams in parallel IP routers.

Localization properties of mode waves in an off-diagonally disordered waveguide system are presented. The disorder is introduced by taking spacings between cores to be random variables. Coupled mode equations are transformed into a matrix eigenvalue problem and eigenvalues and eigenvectors are numerically obtained. Correspondences between the natures of modes and the modal density of states are discussed. The system is divided into several sections which behave effectively as isolated systems. Modes in the entire system are a superposition of modes associated with the sections. A section is divided into several elements, which do not only behave apparently as isolated systems but also couple with each other. When an element includes two cores coupled strongly with each other due to a narrow spacing, modes are strongly localized there. The extent of the modes is almost independent of the disorder of the system. In a system with small disorder strongly localized modes can exist. The modes appear outside the propagation constant band of the ordered system composed of identical cores of equal spacing. Modes near the center of the band are extended over a number of elements and have the relatively large extent. Many modes appear near the center of the band and the modal density of states has a sharp peak there.

Biological object could be trapped by a single laser beam from an optical fiber end inserted at an angle to a sample chamber. Separation/coupling of an individual biological cell was easily achieved using plural optical fibers. From these experimental results, we verify that fiber optic trapping technology can provide new and novel tools for the manipulation of microorganisms and cells without physical contact.

An improvement of the fiber-optic transceiver having both transmitter and receiver functions of optical time-domain reflectometers is examined. The improvement is achieved by introducing an external optical amplifier without changing the previously reported configuration. The characteristics of the transmitted Q-switched pulse and the receiver gain is studied theoretically and experimentally to estimate the performance improvement. It is found that the introduction of the external optical amplifier is a simple and effective way to the performance improvement.

Characteristics of an FBG hydrophone are described under various conditions. The developed FBG hydrophone detects an acoustic field in water with good performances: linear response,high sensitivity,high stability,wide dynamic range as large as 90 dB and wide operation frequency range from a few kHz to a few MHz. A WDM FBG hydrophone consisting of two FBGs in serial connection can detect simultaneously amplitudes and phases of acoustic fields at different points,which in turn allows a directive measurement of an acoustic field in water.

An optical fiber humidity sensor was fabricated forming a nanometer-scale Fabry-Perot interferometer by using the Ionic Self-Assembly Monolayer (ISAM) method. The materials used were Poly R-478 and poly(diallyldimethyl ammonium chloride). Taking advantage of the precision that the ISAM method can achieve in controlling the length of the nano cavity, the length was fit to obtain a maximum variation of 8.7 dB of reflected optical power between 11.3% and 85% RH. The sensor exhibited a fast response time and was able to monitor the human breathing.

A novel technique has been developed for in situ sensing of thin film growth. In this method, a fiber optic probe is placed at an appropriate position in a deposition chamber, and the thin film builds up on the end of the fiber. This film is either the same as on the wafer where deposition occurs, or it bears a fixed relationship to the film on the wafer. By an analysis of the intensity of the light reflected from the film and guided by the fiber, information on the film may be obtained. With interference causing maxima, minima and a point of inflection as the film grows, it is possible to obtain near real time information on the following quantities: the real and imaginary parts of the refractive index of the film, a Gaussian parameter characterizing surface roughness, and the film thickness itself. To demonstrate this technique, we have studied the deposition of silicon nitride films in a CVD reactor and how reactor temperature and reactant flow rates influence film growth. This technique may be applied to measure in situ reflectivity of multi layer films, so that reflectance as a function of temperature and time may be obtained. Because the measurement is simple and direct and the information is optical, we believe that this technique has the potential to supplant quartz oscillators in the measurement of thin film growth.

In this paper, design and experimental results are described about a newly developed highly flexible fiber Faraday effect current sensor using the flint glass fiber as the sensor element. In the new type, a mirror is coated at an end of the flint glass fiber, and light takes round trip transmission in it. By the round trip transmission, the effect of rotation of polarization plane due to the torsion of the fiber is automatically canceled. Because of the low photo-elastic constant of the flint glass fiber, and the automatic canceling of the rotation, the polarization state of light passed through the fiber is stable. Therefore, in the new reflection type, it is not necessary to support the flint glass fiber with a durable circular frame to maintain accuracy. And so, the sensor head is small, light, and can be easily installed to existing power apparatus by winding the flint glass fiber around the current conductor without pulling out or cutting it. Experiments were done to verify the stable characteristics using the developed sensor model. In the experiments, relation between the final output signal of the sensor and shape of the curve of the flint glass fiber were examined. From the experiments, it became clear that the final output is almost perfectly independent on shape of the curve of the fiber. It was also confirmed that accuracy of the sensor conform to the standard of conventional current transducers for protection of power systems in Japan.

The wavelength demultiplexer, using cascaded optical fiber gratings and circulators, was proposed and developed for application to optically amplified wavelength-division multiplexing (WDM) submarine cable systems with 100 GHz channel spacing. Our proposed demultiplexer cannot only achieve high wavelength selectivity, small excess loss and effective allocation of dispersion compensation fibers for each channel, but also be upgraded without affecting other existing channels. By using this demultiplexer, it has been successfully confirmed that 8 WDM channels were demultiplexed even after 6,000 km transmission including separate compensation of accumulated chromatic dispersion in each channel.

A new sensing method for measuring directly flow velocity by using low coherence interference techniques is proposed and demonstrated. In this method, a temporally fluctuating signal, not the Doppler frequency shift, is detected. Theoretical analysis shows that a spectrum of light backscattered from a particle takes a Gaussian form whose width is simply proportional to the flow velocity. The measured velocity is in good agreement with the actual flow velocity derived from the flow rate. The dynamic range of this sensing method is governed by the frequency range of the FFT processor used and is estimated to be 1.4 10-4 14 m/s. The depth position can be adjusted with an accuracy of approximately 30 µm which is determined by the coherence length of the light source. The velocity distribution along the depth is easily measured by changing mechanically the length of the reference arm in the low coherence interferometer.

A correlation-based technique for measuring Brillouin gain spectrum distribution along an optical fiber is proposed, which employs frequency-modulated pump and probe lightwaves. The spatial-resolution of about 40 cm is demonstrated, which cannot be realized by the conventional pulse-based technique.

We will discuss performance optimization of strain and temperature sensors based on long period fiber gratings (LPFGs) through control of the temperature sensitivity of the resonant peak shifts. Distinction between the effects of strain and temperature is a major concern for applications to communication and sensing. This was achieved in this work by suppressing or enhancing the temperature sensitivity by adjusting the doping concentrations of GeO2 and B2O3 in the core or cladding. The LPFGs were fabricated with a CO2 laser by the mechanical stress relaxation and microbending methods. The optimized temperature sensitivities were 0.002 nm/ for the suppressed case and 0.28 nm/ for the enhanced case, respectively. These LPFGs were used for simultaneous measurement of strain and temperature. The result indicates the rms errors of 23 µstrain for the strain and 1.3 for the temperature.

We describe FMCW reflectometry for characterization of long optical fibers by using an external-cavity laser diode as a light source. Since the optical path difference between the reference beam and the reflected beam from the optical fiber under test is much longer than the coherence length of the light source, the reference and the reflected beams are phase-decorrelated. As a result, the beat spectrum between the reference and the reflected beams is measured. In the phase-decorrelated FMCW reflectomety, the spatial resolution is enhanced by narrowing the spectral linewidth of the light source and increasing the repetition frequency of the optical frequency sweep as well as increasing the chirping range of the optical frequency sweep. In the experiments, an external-cavity DFB laser is used as a narrow linewidth light source, and the optical frequency is swept by minute modulation of the external cavity length. Long single mode optical fibers are characterized, and the maximum measurement range of 80 km is achieved, and the spatial resolutions of 46 m, 100 m and 2 km are achieved at 5 km, 11 km and 80 km distant, respectively. The Rayleigh backscattering is clearly measured and the propagation loss of optical fiber is also measured. The optical gain of an erbium-doped optical fiber amplifier (EDFA) is also estimated from the change in the Rayleigh backscattering level in the optical fiber followed after the EDFA.

This paper describes a load carrying test for a concrete pipe designed to study the effectiveness of distributed strain measurement using an optical fiber sensor. We performed a load carrying test on a concrete pipe and attempted to detect the distributed strain inside it using an optical fiber sensor mounted inside the pipe. We confirmed that it was possible to detect the strain in a concrete structure by using an optical fiber sensor after a crack had occurred on the concrete surface. This paper shows that measurement using the optical fiber sensor was effective despite great changes in the strain conditions of the measured object over a short distance.

This paper reports the design and characteristics of an aerial optical drop cable incorporating electric power wires, which was developed for a new π-system. The new system is called the power supply HUB π-system, in which commercial AC electric power is received at a central location of several optical network units (ONUs), and is distributed to each ONU by the aerial optical/electric drop cable. We describe the requirements for the cable, which guarantee a 20-year lifetime. We designed the cross-sectional structure of the cable, based on system requirements and operation requirements, and determined the strength wire type and diameter, based on the optical fiber failure prediction theory and a cable strain requirement. We confirmed that the cables, manufactured as a trial, have stable characteristics, which satisfy the above requirements. The optical/electric drop cables will be introduced in autumn 1999.