**Author details**

Muzahim I. Azawe *Mosul University, Mosul, Iraq* 

#### **8. References**

126 Optical Communication

**7. Conclusions** 

**Author details** 

Muzahim I. Azawe

*Mosul University, Mosul, Iraq* 

**Figure 10.** The influence of gain saturation coefficient on the RIN spectrum of semiconductor laser.

meet the demands for higher bit rates and longer optical communication network.

dynamics of the slave laser is the challenging candidate for secure optical systems.

To illustrate how gain saturation coefficient can alter the RIN spectrum of the slave laser, figure 10 shows this effect. When the gain saturation coefficient was increased, it is noticed that the RIN spectrum at the resonance peak was suppressed and this can be interpreted as damping due to the gain saturation coefficient. We would expect that the strong injection locking phenomenon may give extra damping of RIN peak in addition to the gain saturation coefficient. This has to be verified experimentally. So, both the methods will exhibit large significant RIN suppression, and

This chapter, as I intend to, gave a brief description and theory of strong optical injection and its influence on the characteristics of the slave laser. Secure optical communications can be verified by such operation of the laser. Modulation bandwidth enhancement has been found by numerical simulation of the rate equations. The enhancement was found to be dependent on the injection parameters, frequency detuning and injection strength. Period doubling and relaxation oscillation frequency are the physical mechanisms of bandwidth enhancement by injection locking. Substantial reduction in frequency chirping, and a suppression of 14 dB/Hz in the RIN were observed in the direct modulation injection-locked laser. These characteristics of such a laser are the demands for high bit rate and longer optical communication network. Chaotic

