Dynamic considerations in overmodulation of semiconductor laser diodes

Evaluation of nonlinearity effects in a semiconductor laser under direct overmodulation

“…versus current amplitude), for given frequency It can be observed a dramatic improvement of the distortion evaluation results using the model with hysteresis rather than the static limiter model. The curves are obtained with much smaller computational effort than in [ 2]. Thereason is that after calculating the solution of the rate equations, the present procedure does not need any time consuming numerical Fourier analysis.…”

“…Authors in [2] compared the results obtained by using the simple static limiter model and those derived from the rate equations. Numerical Fourier analysis of the laser time response was used for calculating second and third harmonic distortions with respect to the carrier for two cases : firstly, for different frequencies at a given current amplitude, secondly, for different current amplitudes at a given frequency.…”

Large-signal spurious-free dynamic range due to static and dynamic clipping in direct and external modulation systems

“…Equation (18) can be used to obtain the static-clipping limited large-signal SFDR for both a LD and an external modulator. However, in the case of an LD, SFDR due to (1) dynamic clipping [20]- [24] or (2) laser relaxation oscillation can become predominant. SFDR due to dynamic clipping can be obtained from (16) and (17) as long as the L-I transfer function due to dynamic clipping can be measured, as will be demonstrated in Section IV.…”

“…For example, relative intensity noise (RIN) due to optical reflections [15] or optical beat interference [16]- [19] can be as high as 95 to 120 dB/Hz. In this case, a large-signal modulation may be needed to overcome the high noise floor in order to maintain a required CNR, and consequently clipping-induced IM products may occur [20].…”

“…The analytical result thus obtained can be used as an upper bound on the channel capacity of an optical transmitter. However, it has been recently found that this upper bound is over-optimistic for a LD, because nonlinear distortions (NLD's) due to dynamic clipping cannot be ignored [20]- [24]. The NLD's due to dynamic clipping are different from those caused by laser relaxation oscillation frequency, and can cause a significant turn-on delay in a modulating sinusoidal signal.…”