Cloning an Autonomous Replication Sequence from Aspergillus oryzae

DNA sequence from Aspergillus oryzae genome which, confers on pOK-1 the ability to replicate autonomously in Saccharomyces cerevisiae is described. A hybrid plasmid pOK-1 was constructed from pBR325 and YEp13 fragment containing Leu2⁺ gene. Asp. oryzae DNA and pOK-1 were cleaved with BamHI, ligated and introduced into Escherichia coli. About 600 recombinant plasmids were obtained. One of them transforms S. cerevisiae SHY3 to Leu2⁺ with middle efficiency. The plasmid designated as pSB1–2 contained two BamHI fragments (4.3 kb and 4.1 kb) of Asp. oryzae DNA.     

Measurement of linewidth and FM-noise spectrum of 1.52 ?m InGaAsP lasers

The linewidth of 1.52 ?m InGaAsP lasers was measured as a function of the output power. The result shows that the linewidth is about 15 MHz when the output power is 1 mW. The FM-noise spectrum was also measured in the frequency range from 10 Hz to 100 MHz. The measured spectrum consists of the 1/f-noise and white-noise components. The linewidth calculated from the FM-noise spectrum is in good agreement with the measured value.     

New polarisation-control scheme for optical heterodyne receiver using two Faraday rotators

A new state-of-polarisation (SOP) control scheme using two Faraday rotators is proposed. It features low optical insertion loss and quick response. Experiment shows that the receiver output is stable regardless of drastic SOP changes in the signal.     

Dependence of semiconductor laser linewidth on measurement time: evidence of predominance of 1/f noise

Linewidths of 1.3 ?m InGaAsP lasers were measured by using delayed self-heterodyne set-ups with two different delay-line lengths, i.e. with two equivalent measurement times. It has been found that in high-power operation the linewidth increases as the measurement time becomes longer, and that this dependence is explained well by a calculation assuming that the 1/f noise in the FM noise spectrum is the predominant cause of the spectral broadening. The significance of this fact in coherent optical communications is discussed.     

Vectorial wave analysis of uniform-core optical fibers using anovel boundary integral method

Vectorial wave analyses of uniform-core optical fibers using a boundary integral method that does not use Green's function are presented. The expansion of the electromagnetic field on the boundary, the selection of the weight function, and the method for giving boundary conditions are discussed. By using the formulation obtained, the propagation characteristics of elliptical-core optical fibers are analyzed. The effect of the boundary shape on the numerical results is also investigated through analyses of rectangular-core fibers. It is found that the boundary integral method can easily be applied to solve vectorial wave boundary value problems     

Phase-noise-cancelling dual-frequency heterodyne optical fibre communication system

An experimental 20 Mbit/s PSK heterodyne system using a dual-frequency phase-noise-cancelling scheme has been constructed, and the bit error rate (BER) has been measured. The experimental result shows that the laser phase noise can be cancelled successfully.<>     

Double-stage phase-diversity optical receiver: analysis andexperimental confirmation of the principle

The double-stage phase-diversity (DSPD) scheme features phase-diversity-type optical homodyne detection and phase-diversity-type frequency up-conversion, producing a heterodynelike second intermediate frequency (IF) signal. It has the advantages of both heterodyning and homodyning and is applicable not only to optical, but also to all the electrical and radio communications ranging from VLF to millimeter-wave frequencies. The theoretical analysis of the receiver performance and the experimental confirmation of the principle of the DSPD scheme are described     

A planar chart equivalent to Poincaré sphere for expressing state-of-polarization of light

A planar chart for expressing a state of polarization of an arbitrarily polarized light is proposed. The proposed chart is equivalent to the Poincaré sphere, but has an advantage over the Poincaré sphere in that it can be printed on a flat paper. The characteristics of the proposed chart are investigated. The computer-drawn exact chart is shown with important parameter values. Finally, an example of the application of the proposed chart is described.     

Single-polarization single-mode optical fibers

Strictly speaking, an ordinary axially symmetrical single-mode fiber is a "two-mode" fiber because two orthogonally polarized HE11modes can be propagated in it. This fact results in the instability of the polarization state of the propagated mode when geometrical perturbation exists in the fiber, and also the so-called polarization mode dispersion. These are harmful in some applications of single-mode fibers to communication and measurement. To prevent these adverse effects, single-polarization single-mode (SPSM) optical fibers have been developed. Three basic types of the SPSM fiber are elliptical-core fiber, stress-induced birefringent fiber, and side-pit fiber. This paper describes the principles of these three types, performance obtained experimentally, theoretical approaches, and measurement techniques related to the SPSM fibers. Finally, relevant technical tasks in the future are mentioned.