The introduction of high-speed services for fiber-optic access subscribers has led to a huge growth in data traffic. The rapid diversification of services means that next generation networks must be built quickly, economically and reliably.
A high temperature laser allows us to eliminate the thermo-electric cooler conventionally needed in a transmitter module, which results in reductions in cost, power consumption and size. Moreover, a high-power laser provides a wide tolerance when coupling optical fibers. In addition, a high-power pump laser is needed to realize a wide-band and high-power erbium-doped fiber amplifier. This makes high-performance laser chips one of the keys to achieving highly reliable and cost-effective systems.
In terms of laser reliability, we must clarify the degradation mechanism and postpone or suppress degradation if we are to achieve a reliable high-performance laser. We have analyzed degraded lasers using the optical beam induced current (OBIC) technique. When there are nonradiative recombination centers in the degraded region, the OBIC intensity decreases with increases in recombination density. This technique has the advantages of being non-destructive and highly sensitive. In addition, it provides high space resolution in degradation analyses.
The OBIC is measured through the window of a transistor outline (TO) can before and after aging. Then, by using the same LDs we can detect an OBIC change for several aging times. We can both detect the degraded region and layer, and estimate the degree of laser degradation by employing the relative OBIC intensity prior to aging. This OBIC technique is useful for analyzing the degree of laser degradation.
Moreover, the incident wavelength can be changed by changing the optical source in the OBIC measurement setup, which in turn changes the absorption layer and the penetration distance. Some degraded laser layers are reveled by using these several wavelengths absorbed in different layers. In addition, degradation in the waveguide interior is detected by using an incident wavelength with long penetration. Thus, by monitoring the OBIC intensity at several wavelengths as well as before and after aging, we are able to discuss sudden and wear-out laser failures. In our presentation, we will introduce examples using the OBIC technique that contributed to the improvement of laser reliability.