The net result is that the increasing demand for bandwidth mirrors a similar demand for laser diode modules. The problems for the industry are, first, that lasers need testing at several stages from raw chip to finished module and, second, that testing laser diode modules is quite complex. You can perform a test at the chip level provided the test strategy addresses power dissipation issues by using a pulsed current sweep rather than a DC test. After the wafer has completed processing it is cut into bars or chips. These are then polished to improve the optical interface to a degree that allows optical testing.
Many manufacturers elect to use pulse mode DC test to minimise the power dissipation issue.
The bonding of the laser to a chip carrier greatly increases the thermal mass and eases the power dissipation issue. This is also the first stage at which you can measure the characteristic wavelength of the laser. Each mounting or bonding step has the potential to induce mechanical and electrical failure mechanisms. Also, the magnitude of back reflections re-entering the laser cavity will affect the stability of the laser. You need to test the unit again to ensure only known good devices pass on to the costly burn-in process.