Single-mode hole-assisted fiber as a bending-loss insensitive fiber

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.     

Single-mode optical fiber connection to high-silica waveguide with fiber guiding-groove

Single-mode optical fiber connection to high-silica ridged waveguide formed on a silicon substrate is experimentally described. Fiber alignment and fixing processes are easily accomplished using a guiding groove fabricated at the waveguide end. An average connection loss of 0.4 dB was achieved. Optimum groove configuration, temperature stability of fiber connection, and polarization maintaining characteristics are discussed with experimental results.     

关于单模光纤段差的研究

本文研究段差的形成机理,并实际模拟段差的形成,为解决单模光纤段差提供了理论和实际依据.     

Single-mode fiber design for long haul transmission

By using simple yet accurate approximations for the propagation characteristics of a single-mode optical fiber, we obtain a simple model for the total loss and chromatic dispersion of single-mode fiber transmission lines as a function of the operating conditions such as splice offset, microbending loss, bends, etc. This model is then applied to typical cases of terrestrial and submarine systems and we obtain single-mode fiber designs which are stable with respect to slight operating condition changes for both 1.3 and 1.55 μm wavelengths. It appears that the same fiber can be used at 1.3 μm for both terrestrial and submarine systems, and even for 1.55 μm terrestrial systems if monochromatic sources become available at this wavelength. A general comparison between the two wavelengths is carried out and shows under which conditions the 1.55 μm wavelength is of practical interest. It is emphasized that the availability of monochromatic sources at 1.55 μm would make a major breakthrough for the repeater spacing.     

Single-mode fiber OTDR: Experiment and theory

An OTDR measurement technique with an end detection dynamic range of 63 dB is described for use with single-mode fibers. A theoretical analysis of single-mode fiber backscattering is presented which predicts loss penalties in single-mode OTDR's compared with multimode fibers. The prediction of the critical power levels of about 3- 4 W for the onset of nonlinear effects in fibers is shown to be in good agreement with experiment. Fusion welded splices do not demonstrate significant backscattered power.     

Single-mode optical isolator at 1.3 ?m using all-fibre components

An optical isolator for use at 1.32 ?m has been fabricated using standard communication-grade single-mode fibre as an optical rotator fitted with high-birefringence fibre pigtails containing an in-line tapered fibre polariser. A novel adjustment procedure ensures isolation levels are limited only by the polariser extinction ratio. Isolation levels in excess of 21 dB have been recorded with an insertion loss of less than 3 dB.     

Single-mode fiber directional couplers fabricated by twist-etching techniques (stabilization)

Rugged single-mode fiber couplers have been fabricated by two different techniques: 1) twist-etch RTV potting, and 2) twist-etch gel glass potting. The performances, in terms of optical stability, mechanical ruggedness, and lifetime, are compared between the couplers made by these two techniques, and also with those of the original twist-etched (bottle) coupler reported earlier.     

Single-mode fiber WDM unit for duplex subscriber link using asubstrate with embossed alignment grooves

A wavelength division multiplexing (WDM) unit for single-mode fiber (SMF) duplex transmission, with light source, photodiode (PD), and WDM coupler arranged on a common substrate, is described. Using a tolerant optical design, the optical elements, e.g. lenses and fibers, are positioned in embossed high-precision V grooves without active adjustments. Only the light source, a laser diode (LD) or an edge-emitting LED (ELED), must be aligned for optimum coupling and fixed by laser welding. Typical values of LD-to-fiber and fiber-to-PD coupling loss and crosstalk are 5 dB, 1.2 dB, and -44 dB, respectively. Hence, in spite of the potentially low-cost design, the optical performance of the device is virtually competitive with separated transmitter and receiver units     

Single-mode optical fiber with arbitrary refractive index profile: Propagation solution by the Numerov method

The Numerov integration scheme is discussed in its application to calculation of the propagation characteristics of single-mode optical fibers with arbitrary refractive-index profiles. The technique can be made highly accurate, with modest computational requirements. Examples are given for simple step fiber, W-fiber with rectangular central dip, and for depressed-clad fibers. For the depressed-clad fibers, experimental results are compared with predictions for dispersion from the Numerov method.     

Single-mode fibre connectors

A low-loss detachable connector has been fabricated for single-mode optical fibres. It consists of a pair of plugs accommodating fibres to be joined and a sleeve provided with ball-bearing arrays to align the plugs. The average connecting loss is reduced to as low as 0.5 dB, including fibre end reflection.     

Single-mode operation characteristics of a self-injection seededFabry-Perot laser diode with distributed feedback from a fiber grating

We study the operational characteristics of a self-injection seeded laser diode in an external cavity consisting of a fiber Bragg grating. The distributed feedback (DFB) of light in the grating provides an additional tolerance of frequency detuning in mode selection. The spectral characteristics at different operating frequencies and feedback rates have been investigated. Wavelength tuning has also been realized by applying compressive and tensile strain to the grating and a tuning range of 11.6 nm has been obtained     

Wide-beam propagating fiber for inline optical components

A new technique is proposed for integration of bulky optical components by means of a specific graded-index fiber in which the fundamental mode has a large mode-field diameter (MFD). A wide-beam propagating (WBP) fiber with the field diameter as large as 60 /spl mu/m was successfully fabricated, which will enable bulky optical components that have no wave-guiding structures to be embedded into a fiber circuit without any lenses. It was confirmed that a 5-mm-thick silicon plate, for example, can be integrated into the fiber with a loss of less than 1 dB. A hemispherically ended WPB fiber for much longer bulky components is also proposed.     

Single-mode laser frequency modulation

This paper presents an analysis of the frequency response of single-mode laser frequency modulation. The method employed is based on the combined concepts of an active Fabry-Perot interferometer and of internal phase modulation, and is very transparent. The calculation of the sideband amplitudes and phases of the laser output reveals two main regions of the frequency response: for modulating frequencies lower than the cavity mode spacing the laser generates an ideally frequency-modulated signal. At higher frequencies the sideband amplitude versus modulating frequency shows an oscillatory behavior. Here, the response is mainly determined by the cavity mode spacing frequency and by the position of the modulator within the cavity. Comparing the theoretical results with previously reported experiments, very good agreement was found.     

Single-mode optical-fibre ribbon cable

A single-mode optical-fibre ribbon cable was manufactured and investigated. An average cable loss of 0.45 dB/km and average fusion mass-splice loss of 0.35 dB have been achieved at a wavelength of 1.3 ?m. These results indicate that single-mode-fibre ribbon can be applicable to large fibre count transmission.     

Single-mode optical fibre switch

A 1 × 4 single-mode optical fibre switch is described which has an insertion loss of less than 0.5 dB with repeatability of ±0.01 dB and crosstalk less than ?70 dB.     

Single-mode fiber-film directional coupler

Directional coupling has been observed both from a single-mode fiber to a single mode planar polymer waveguide and vice versa. The fiber coupler was prepared by polishing. The matching of propagation constants was achieved by using a polymer film only a few hundred nanometers thick.     

Single-mode fibre pressure sensitivity

The pressure-induced retardation in a sample of single-mode fibre cable has been measured. The pressure sensitivity of the uncoated fibre was found to agree with the theoretically expected value. Application of a silicone rubber coating reduced the sensitivity by over 50%. No pressure sensitivity was measured when a loose-fitting tube was extruded around the coated fibre.     

Single-mode digital transmission technology

Single-mode fiber technologies, including fibers, semiconductor devices and transmission systems, are delineated. Transmission experiments up to 1.6 Gbit/s in the 1.3- and 1.5-µm bands show the feasibility of applying single-mode fiber application to high data rate systems.