Nonlinear Distortion Analysis of Directly Modulated ... - 연세대학교

locking to suppress nonlinear distortion, the analog system performance can beimproved greatly.A. Injection Locking Characteristic AnalysisTo investigate the locking characteristics in the injection locked laser, it isneeded a laser model which contains the external light injection effects. Theequations below are adequate for this purpose [17]. These rate equations aresimilar to the eqn. 2-1, but contain E-field characteristics of external lightinjection.dSdt( N − Nt) S βNΓg0S − + + 2KcS ⋅ Sinjcos( Φ − Φ)(1 − εS)τ τ=injp n3-1(a)dΦdt1 ⎪⎧( − ) 1 ⎪⎫=⎬ − 2 ∆ + sin( Φ − Φ)2α N NStinj⎨ − π f Kcinj⎪⎩ (1 − εS)τp ⎪⎭S3-1(b)dNdtI= − g ( N − N ) S −qVaN0 t3-1(c)τnIn these equations, Φ inj indicates the injection photon phase, and K c is thelongitudinal mode spacing that is related to the coupling of externally injectedwave. ∆f is the frequency difference between the ML and SL: the valuesubtracting the SL frequency from the ML frequency. The other parameters arethe same as eqn. 2-1.Based on these rate equations, small signal analysis is performed at first.By small signal analysis, the stable locking range can be obtained [18]. In caseof injection locking, the laser locking is determined by the frequencydifference, ∆f and the power ratio defined as the ratio of the ML power to the22