Abstract:
PURPOSE: To measure the nonlinear refractive index of an optical fiber by equipping only one of a pair of pulses with such a power as to cause a nonlinear effect inside the fiber, and measuring the phase shift between the two pulses of the pair. CONSTITUTION: A series of pulses are emitted by a laser L, passed through a variable damper AV1, and divided into two identical pulse trains by a coupler C1. The two pulse trains are transmitted in the opposite directions along a loop AS, and one of them is damped largely by a variable damper AV2 before coming into a fiber F. Another pulse train passes the polarization control device PC2, which compensates the complex refraction of the loop AS, and it goes out from the port O1 of the coupler C1 with the power possessed by pulses which are re-coupled after transmission along the loop. The pulses returned to the coupler C1 have the same intensity, but only one of them exhibits a vital phase shift owing to self-phase modulation.
Abstract:
PURPOSE: To obtain deformation-limited ultra-short light, pulses, used for a high-bit-rate transmission system, by direct modulation of a semiconductor laser. CONSTITUTION: The ultra-short light pulses are obtained from pulses having pulse width exciting only the 1st peak of relaxation oscillation of the cavity of the laser 1, and the cavity is so adjusted that pulse parts overlapping with the inside of the cavity become long enough to cause structural interference. The pulses emitted by the laser 1 are passed through a fiber 8 having negative high dispersion to compensate phase effect by a chirp.