Theoretical analysis of mode-competition noise in modulated laser diodes and its influence on the noise performance of fibre links

Abstract

Abstract. We analyze the mode competition (MC) phenomenon in sinusoidally modulated laser diodes and the associated noise. Contribution of MC noise to the noise performance of directly modulated fiber links is evaluated in terms of the noise factor (NF) of the link. MC is analyzed through intensive simulation of laser dynamics and noise basing on a multimode rate equation model that takes into account both symmetric and asymmetric suppressions of the cross-modal gain. Variations of the MC relative intensity noise (RIN) of both the total output and the oscillating modes with modulation conditions are investigated. The obtained results showed that the modulated signal has six distinct waveforms depending on the modulation conditions. The modulated laser oscillates in single mode when the signal is continuous, and converts into multimode when the signal is pulsing. Contribution of MC noise to NF of the link increases with the increase in the modulation depth and with the decrease in the modulation frequency, except when the signal has period doubling. This contribution is negligible under high modulation frequencies when the laser signal is continuous and uniform, and is most enhanced (~53 dB) under low-modulation frequencies when the signal is pulsing and superposed with non-uniform relaxation oscillations.

Intensity noise in ultra-high frequency modulated semiconductor laser with strong feedback and its influence on noise figure of RoF links

“…On the other hand, noise is a primary factor affecting efficiency of RoF links. It is desirable that the smaller is the noise factor and the higher is the efficiency of the link [14]. The intensity noise of semiconductor lasers is caused by random fluctuations in carrier and photon recombination and generation processes, which result in instantaneous time variations in the carrier and photon densities [15].…”

Direct Modulation Performance of Quantum Well Semiconductor Laser Diodes Operating in Multimode

“…(8)(9)(10). Assuming wavelength of the central mode to be λ 0 with p = 0, the other longitudinal modes are defined asp = 0, ±1, ±2, … (11) Here we consider λ 0 lies at the center of the gain spectrum and neglects any wavelength shift due to other effects [17,18]. The noise is generated due to the temporal photon number fluctuation, which is defined as δS(t) = S(t)-S avg, with S(t) = ∑S p being the total photon number.…”

“…With different modulation depths and frequencies, we may get different types of laser output signals like the continuous waveform or the pulsing waveform [9]. These signal waveforms are associated with different types of intensity noise like, the harmonic distortion that causes mode coupling noise or chaos [6,10,11]. Bakry et al in [12] characterize the InGaAsP based near-infrared laser diodes under modulation at the resonance frequency and get changes in the mode coupling from anticorrelation to positive correlation with an increase of the modulation depth.…”

Enhancing Modulation Bandwidth of Semiconductor Lasers beyond 50 GHz by Strong Optical Feedback for Use in Millimeter-Wave Radio over Fiber Links

“…In additions, harmonic distortions and noise associated with high frequency modulation [3][4][5][6][7] of the laser limit the gain and dynamic range of laser-based fiber links. [8][9][10] The technique of injection locking has been reported by several groups to enhance the modulation bandwidth of laser diodes, 11,12) and a record of 40 GHz was demonstrated by Chan et al 13) External optical feedback (OFB) has been shown to be an alternative and cost-effective technique to increase the modulation bandwidth of semiconductor lasers, depending on appropriate choices of the system parameters. [14][15][16][17][18][19][20][21] The resonant enhancement over 30 dB of the modulation response was demonstrated in mmwave bands.…”