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We propose an optical switch that rotates an MCF set in a cylindrical ferrule. We show the loss characteristics and examine the factor of the excess loss focusing on an offset between the each core.

We investigated the conditions that cause a connector damage during a high-power transmission in an optical connector with house dust on its endface. In this paper, to examine the connector conditions that cause the connector damage, we focused on optical characteristics, such as insertion loss and return loss, dust attachment pattern, and optical power. We show the relationship between the connector damage and the MFD of the fiber used in telecommunication network when house dust is used as a contaminant. Moreover, we show the threshold value of the input power level needed for damage to occur to a connector with house dust on its endface when that power is interrupted completely. We also describe the operating procedure for a secure high-power transmission, where the procedure consists of connector cleaning, connector endface observation, and insertion and return loss measurements. We show that it becomes possible to completely remove dust, which we could not remove with a cleaner alone, by using an air duster in combination with a cleaner. We also show that an optical connector cleaned with our proposed procedure, which exhibited an insertion loss of less than 0.5 dB and a return loss exceeding 45 dB, tolerated a high optical power of 5 W.

We experimentally investigate the cutoff wavelength shortening effect that occurs when the cladding diameter is reduced. The influence of coating thickness, and thus, cladding diameter, on the transmission loss is also discussed. We derive an empirical model of cutoff wavelength and transmission loss as a function of the cladding diameter and coating thickness. The empirical model reveals that a further reduction in the cladding diameter of step index type bending-loss insensitive fiber (BIF) is possible. The validity of the proposed BIF design is confirmed using a 70-μm cladding diameter BIF and jumper cords. This BIF enables us to construct optical fiber networks with higher reliability.

We investigate the design and characteristics of a single-mode and low bending loss HAF both numerically and experimentally. An air filling fraction S is introduced to enable us to design a HAF with desired characteristics more easily. We show that we can expect to realize a single-mode and low bending loss HAF by considering the S dependence of the bending loss α b and cutoff wavelength λ c as well as their relative index difference Δ dependence. We also show that the mode-field diameter (MFD) and chromatic dispersion characteristics of the single-mode and low bending loss HAF can be tailored by optimizing the distance between the core and the air holes. We also investigate the usefulness of the fabricated HAFs taking the directly modulated transmission and multipath interference (MPI) characteristics into consideration. We show that the designed HAF has sufficient applicability to both analog and digital transmission systems. Our results reveal that the single-mode and low bending loss HAF is beneficial in terms of developing a future fiber to the home (FTTH) network as well as for realizing flexible optical wiring.

We discuss the applicability of photonic crystal fiber (PCF) with a uniform air-hole structure to high-speed and wide-band transmission over conventional telecommunication bands. We design the PCF to maximize the effective area by utilizing the macro-bending losses of the fundamental and first higher order modes (HOM) and clarify that a single-mode and low bending loss PCF can realize the largest effective areas of 133 and 157 mum2 for transmission over the 1260-1625 nm (O ~ L bands) and 1460-1625 nm (S ~ L bands) wavelength ranges, respectively. We then investigate the impact of the designed PCF on nonlinearity reduction over a wide wavelength range and show that the PCF helps to increase the maximum channel power in a wavelength division multiplexing system. We also discuss the distributed Raman amplification (DRA) characteristics of PCF with a large effective area. Our results show that we can expect to improve the signal to noise ratio with DRA in spite of the low nonlinearity of the designed PCF. Dispersion compensating fiber (DCF) with a conventional W-shaped index profile is designed to compensate for the relatively large dispersion of the PCF, and we show that the designed DCF can extend the dispersion compensation bandwidth from 1340 nm to 1650 nm for a 40 Gbit/s transmission. Finally, we clarify the applicability of the large effective area PCF with the uniform air-hole structure as a high-speed and wide-band transmission medium.

This paper describes the distributed Raman amplification (DRA) transmission characteristic in an optical fiber both numerically and experimentally. The paper clarifies the relationship between optical fiber parameters and DRA transmission performance with regard to the signal-to-noise ratio (SNR) characteristics and nonlinear impairments. These relationships can be successfully discussed, taking account of various fiber parameters, including Raman gain efficiency, the attenuation coefficient at signal and pump wavelengths, the Rayleigh scattering coefficient, and the nonlinear refractive index, as a function of the relative index difference in an optical fiber. An example of an optimum fiber design for a DRA-based dense-wavelength-division-multiplexing (DWDM) transmission system is also discussed.

A systematic optical emission spectroscopy (OES) study was carried out to enhance the deposition rate of microcrystalline silicon (μc-Si:H) with conventional r.f. plasma-enhanced chemical vapor deposition (r.f. PECVD). Among the various plasma parameters, the combination of total pressure, r.f. power, electrode distance and cathode heating was effective to promote the deposition rate without deteriorating the film crystallinity. Strong correlations among the OES intensity, SiH, intensity ratio, I H α / I Si* , deposition rate and Raman intensity ratio, I μc-Si / I a-Si were confirmed in the case of r.f. SiH 4 and H 2 PECVD. A relatively high deposition rate was achieved of ∼5 A/s in the μc-Si:H film growth by optimizing the deposition parameters. The effects of higher pressure, higher r.f. power, inter electrode distance and cathode heating (SiH 4 gas heating) are demonstrated in the growth of μc-Si:H from strong H 2 -diluted SiH 4 by a conventional r.f. glow discharge.

We describe the applicability of photonic crystal fiber (PCF) with an enlarged effective area Aeff to a distributed Raman amplification (DRA) transmission. We investigate the DRA transmission performance numerically over a large Aeff PCF taking account of the signal-to-noise ratio (SNR) improvement RSNR in the S, C, and L bands. We show that an RSNR of 3dB can be expected by utilizing DRA with a maximum pump power of 500mW when the Aeff of the PCF is 230µm2.

We investigate numerically the applicability of photonic crystal fiber (PCF) with a uniform air hole structure as a wide-band transmission medium. We show that accumulated dispersion over the PCF can be reduced effectively by optimizing the index profile of dispersion compensating fiber (DCF). We also show that a bandwidth of more than 300nm will be available for 40Gbit/s NRZ transmission by using the PCF as a transmission medium instead of conventional 1.3μm zero-dispersion single-mode fiber (SMF).

The impact of multi-core crosstalk on far-field pattern (FFP) measurement is clarified numerically and experimentally. We show that the neighboring core angle against the scanning plane greatly affects the FFP and mode-field diameter characteristics.

The reliability of a pure silica core single-mode fiber with long-term exposure to continuous wave (CW) high-power laser light is reported. It is found that the optical loss in the 0.6-1.6-/spl mu/m region and the Raman spectrum remain unchanged after 1900 h of exposure to 8-W CW laser light at 1.48 /spl mu/m. The nonbridging oxygen hole center concentration generated by 1900 h of exposure is estimated to be below our detection limit of 2/spl times/10/sup 12/ cm/sup -3/.

We have succeeded in reducing the PMD of PCF to 10% of its initial value by periodic bidirectional twisting without loss increasing and structural deformation. A PCF with PMD of 0.03 ps/rkm has been obtained.

We describe the dopant dependence of Raman gain in germanium- and fluorine-doped optical fibers. We clarify, both theoretically and experimentally, the effective Raman gain characteristic in an optical fiber, which is closely related to the fiber's refractive-index profile and electromagnetic field profile. We also show that this experimentally determined relationship can be used to evaluate the effective Raman gain characteristic in a germaninum- or a fluorine-doped optical fiber with an arbitrary index profile.

A photonic crystal fibre (PCF) with polarisation mode dispersion (PMD) of 0.03 ps/rkm was obtained by unidirectional twist. The work was also successful in reducing the PMD of the PCF to 10% of its initial value by periodic bidirectional twisting without loss increasing and structural deformation.

Low temperature growth of hydrogenated chlorinated crystal silicon [µc-Si:H(Cl)] films from dichlorosilane (SiH2Cl2) by conventional rf glow discharge (13.56 MHz) is investigated. The role of chlorine and hydrogen in crystal formation is discussed in terms of studies on gas phase and surface chemistry through film deposition, plasma diagnostics and in situ monitoring of the surface reaction. The electron temperature in the SiH2Cl2/H2 plasma significantly depends on not only pressure but also substrate temperature. The surface termination species depend on substrate temperature and hydrogen flow rate. The growing top surface is mainly terminated by chlorine as SiCl n (n=1, 2). Specific features of crystal formation at low temperatures from SiH2Cl2/H2 plasma are demonstrated and compared with those from SiH4/H2.

The crystallinity at the initial growth stage of hydrogenated microcrystalline silicon (µc-Si:H) was greatly improved on Corning #7059 glass substrate with dichlorosilane (SiH2Cl2) as the starting gas using conventional (13.56 MHz) capacitively coupled plasma-enhanced chemical vapor deposition system. Deposition studies examined film thickness, substrate temperature, total pressure, electrode distance and H2-dilution conditions as variables. Through Raman spectroscopy, atomic force microscopy (AFM), spectroscopic ellipsometry, X-ray diffraction (XRD) and Mie scattering measurements, it was found that ∼20 nm sized crystalline Si particles were formed in the plasma region, resulting in the enhanced crystallization from the initial growth stage. The growth kinetics of µc-Si:H from SiH2Cl2, compared with that from SiH4, is described.

Optical wiring conditions are investigated numerically and experimentally with a viewpoint of MPI induced transmission performance degradation. We reveal the impact of the interval of the bending portion on MPI degradation for the first time.