# OptiSystem Tutorials

## LED Modulation Response

The frequency response of an LED is determined by the carrier dynamics (and therefore is limited by the carrier lifetime Tn) and the parasitic capacitance of the LED (described by the RC constant TRC[2]. If a small, constant forward bias is applied, the influence of the parasitic capacitance of the LED can be neglected. The…

## Semiconductor Laser Modulation Response

When using a directly modulated laser for high-speed transmission systems, the modulation frequency can be no larger than the frequency of the relaxation oscillations. The relaxation oscillation depends on both carrier lifetime and photon lifetime. The approximate expression of this dependence is given by: The relaxation oscillation frequency increases with the laser bias current. In…

## Semiconductor Laser—Large Signal Modulation

The large-signal characteristics are related to the digital on/off switching of the laser diode. First, we will demonstrate the delay time required to achieve the population inversion to produce the gain. Second, we will demonstrate the typical for the direct modulation of semiconductor laser amplitude and phase modulations. For the laser which is completely turned…

## Chirp in Mach-Zehnder Lithium Niobate Modulators

The objective of this lesson is to demonstrate the relation between the voltage applied to the modulator arms and the chirp in the output for MZ Lithium Niobate modulators. Chirp is a critical element in high bit rate lightwave systems because it can interfere in the limit of the system distance [1]. External modulators offer…

## LED Spectral Distribution

The spectral distribution of the optical source determines the performance of the optical system through the dispersion [1], [2]. The spectral distribution of the LED is determined by the spectrum of spontaneous emission, which typically has a Gaussian shape. In the 1300-1500nm region, the spectral widths of the LED vary from 50 to 180nm. The…

## Semiconductor Laser L-I Curve

The Light – Current (L-I) curve characterizes the emission properties of a semiconductor laser as it shows the current that needs to be applied to obtain a certain amount of power. We will show a L-I curve of our laser rate equation model with default Ith = 33.45mA . The project is depicted in Figure 1.…

## Laser Noise and Linewidth

Laser Intensity Noise.osd (see Figure 1) shows the laser spectral in CW operation at several power levels. Figure 1: Laser Intensity Noise The laser exhibits fluctuations in its intensity, phase, and frequency, even when the laser is biased at a constant current with negligible current fluctuations (see Figure 2). Figure 2: Laser Noise

## Vertical-Cavity Surface-Emitting Laser – VCSEL Validation

The purpose of this lesson is to compare the simulation results of the VCSEL laser component with the published articles [1] and [2]. The first part of the lesson will compare the LI and IV curves of the component for different input parameters with the experiments presented in [2]. The second part of the lesson…

## Using the Laser Measured Component

The purpose of this lesson is to demonstrate how to obtain the laser physical parameters from measurements. Case 1: Setting the measured values Z, Y, P1 and Ith to obtain the correspondent physical parameters: Using the measured values obtained in [1], set up the measured tab in the laser component: P1 = 1.36 mW @…

## Effects of Group Velocity Dispersion (GVD) on Gaussian Pulse Propagation

To demonstrate the influence of the group (GVD) velocity dispersion on pulse propagation in optical fibers in “linear” regime. The basic effects related to GVD are: GVD induced pulse broadening GVD induced pulse chirping Pulse compression The equation, which describes the effect of GVD on optical pulse propagation neglecting the losses and nonlinearities, is [1]:…