Optical source driver circuit with controllable termination

A driver circuit for a laser diode or other optical source comprises a controllable termination for a transmission line coupled between the driver circuit and the optical source, with the controllable termination being switchable between at least first and second termination configurations. The transmission line comprises a first conductor coupled to a first terminal of the optical source and a second conductor coupled to a second terminal of the optical source, and the driver circuit comprises a first current source configured to drive the first conductor, and a second current source configured to drive the second conductor. By way of example, the first termination configuration may comprise an alternating current (AC) termination configuration and the second termination configuration may comprise a direct current (DC) termination configuration.