The optical device includes a Fabry-Perot laser positioned on a base. A modulator is also positioned on the base so as to receive the output from the laser. The modulator is a Franz-Keldysh modulator that uses the Franz-Keldysh effect to modulate light signals. The laser and modulator are configured such that the modulator modulates the output from the laser and also such that the temperature dependence of the modulator tracks the temperature dependence of the laser.