SU1505389A1 - Method of pulse-frequency modulation of single-mode injection laser - Google Patents

Abstract

The invention relates to methods for partly modulating radiation and can be used in optical communication systems. The purpose of the invention is to increase the stability of the magnitude of the generation frequency shift. The method is based on shifting the generation frequency of a SINGLE-MODE injection laser covered by optical feedback by a given value of f by giving a control current pulse, which returns the fraction of the power fj to the laser resonator, which is determined by the H31 ratio 0.05 7 I (H ) L nr, / 2f, where L is the optical length of the feedback, C is the speed of light in vacuum, D is the optical length of the laser resonator, "is the amplitude-Phase ratio of the injection laser, and n is an integer. The application of the method makes it possible to increase the stability of the magnitude of a given shift of the generation frequency of the injection laser by more than an order of magnitude. . 1 il. h g (/

Description

The proposed method of frequency-impulse modulation of radiation from a single-mode injection laser can also be used in optical coherent communication systems, in particular in fiber-optic to occident communication, using heterodyne of the received optical radiation.

The aim of the invention is to increase the stability of the magnitude of the generation frequency shift.

The proposed method is illustrated by a drawing.

Single-mode injection laser 1 connected to the source 2 of the injection current. The laser resonator is bounded by reflective ends 3 and 4. A source 5 of control current pulses is also connected to the electrode of the injection laser 1 along with the source 2 of the injection current. On the side of the end 3, an external resonator 6 is optically connected to the injection laser 1, which forms optical feedback and consists of its object 7, the optical fiber 8, the optical fiber attenuator 9, for example, an attenuator on a fiber optic flexure, and the reflective element 10, From the side of the end face 4 to the laser 1 laser SP

about

SP

with

00

kn polkl1 chen fiber specodod 1 I line sp zi. Physical ducts. Tlementon following: 1 - long resonator, 1 - length of the gap between laser 1 and matching lens 7, 1 (- lens length 7, Ij - air gap between lens 7 and fiber optic 8, 1 - fiber length 8

The proposed method is implemented as follows;

A single-mode injection laser, when passing through an injection laser I from source 2 in the absence of optical feedback (an isolated laser), generates a laser resonator, formed by reflective ends 3 and A, of optical radiation propagating at both sides of ends 3 and 4. The frequency is proportional to (I - Inop) where I then the threshold value of the injection current

about Sod - Inop),

 L d

where S 7- - torsion module tsnon- dl „

Noah characteristics.

The generation of an injection laser 1 covered by optical feedback can occur in several modes of external resonator 6, one of which, called the dominant one, dominates in intensity over the others. Optical feedback occurs as follows. Optical radiation from the end 3 of the single-mode injection laser 1 enters through the matching lens 7 into the optical fiber 8, passes through the fiber optic attenuator 9 and at the output of the optical fiber 8 reflects from the reflecting element 10, the optical fiber 8 again passes and the optical fiber optical attenuator 9 and through the lens 7 is fed back to the laser resonator, limited by the reflection by the ends 3 and 4.

Dol g | the power of the radiation, the possibility of BpapiaeMOfo back to the laser resonator, is removed by the expression

Ros P Rl

where RA is the power taken from a toril of 3 11H (to itiKMinor o lasers 1;

R

five

0

Of - mspinogt. radiation, from the nose to the laser cutter ..

The value of n can be changed by the mismatch of the injection laser 1 and the external resonator 6 by defocusing the matching lens 7 or by introducing additional losses in the external resonator 6 by means of a fiber optic attenuator 9o

Example. A single-mode injection laser of type 1 ILPN-202 generates at a frequency of S 230000 GHz (L “1.3 μm). Together with a constant injection current I 100 mA (Inop 50 mL), control pulses with an amplitude IA of 0.07 mL are supplied to the electrode of the injection laser 1. The injection current I is stabilized with an accuracy of 10 μA, the temperature of the substrate of the injection laser is stabilized with an accuracy of 5 0.005 ° C. The injection laser I is covered by optical feedback with an optical length L 115 cm.

The proportion of the radiation power returned by optical feedback to the laser resonator was 17 4-10, the optical length D of the laser resonator is 0.04 cm, the coefficient is 0 4,

Claims (1)

The slope S of the modulation characteristic of the injection laser 1 covered by optical feedback was obtained equal to S 200 MHz / mA, the slope So of an isolated laser equal to SQ 1.8 GHz / mA, Q Thus, an increase in the stability of f / uf by 9 times was obtained. Invention Formula Method of pulse-frequency modulation of radiation of a single-mode injection laser covered by optical feedback, based on shifting its generation frequency by a predetermined value f by supplying a control current pulse, characterized in that, in order to increase the stability of the magnitude of generation frequency shift , return by means of optical feedback to a laser. a resonator is a fraction of the power n, the value of which is chosen from  0.05 P i D / lLVl + a), L | -, where c is the speed of light and vacuum; D is the optical length of the laser resonator; five five : "... five CX is the amplitude-phase coupling coefficient of the injection laser; 7 J 7ff P 1l li li h 1505389 optical reverse connection; integer. YU