Low-cost optical sub-assemblies for metro access applications
The fiber optic communications industry is experiencing significant change as datacom 10 Gb/s Ethernet (10 GbE) networks merge with telecom SONET 10G networks in the drive to reach metro access applications. Lower data rate (1G Ethernet, 1G and 2G fiber channel, and SONET OC-48) applications have already merged to some extent as various versions are available within the SFF or SFP standard transceiver form factors. Traditional 10 Gb/s optical subassemblies (OSAs), developed for SONET OC-192 applications, used variations of the expensive butterfly type package. However, smaller form factor modules (such as the XFP that uses SFF optical connectors and LC duplex optical connectors) require much smaller OSAs. To meet the size limitation of packaging 10G OSAs into the XFP transceiver and also meet the 10 GbE market challenge of providing low-cost solutions, new 10 Gb/s OSA components are needed.
A 25 Gbit/s Transmitter Optical Sub-Assembly Package Employing Cost-Effective TO-CAN Materials and Processes
A cost-effective 25 Gbit/s directly modulated transmitter optical sub-assembly (TOSA) employing transistor outline (TO)-CAN materials and processes is demonstrated. A high speed distributed feedback laser diode (DFB LD) chip used in the TOSA is characterized by a directly high frequency probing measurement and an equivalent circuit model according to the measurement result. Using a TOSA package with TO-CAN structure and applying the deduced equivalent circuit model of the DFB LD chip in the simulation, a modified TOSA is proposed. The parasitic effect of bonding-wire and the gap induced in die bonding process is studied comprehensively to achieve an optimum configuration. Based on the simulated result, the proposed TOSA is fabricated through a conventional TO-CAN and TOSA fabrication process. The measured results show that the TOSA exhibits a 3-dB bandwidth of 18.7 GHz and a clearly opening eye diagram of 25 Gbit/s. This developed TOSA is potential for use in the next generation fiber network of 25 Gbit/s or 100 Gbit/s due to advantages of cost-effective design and mass production capability.
Temperature-humidity-bias behavior and acceleration factors for nonhermetic uncooled InP-based lasers
The stability of uncooled InP-based laser diodes in humid ambients was studied. Nonhermetic devices were aged at two different temperatures and humidities at a constant current and at one temperature and humidity at six different drive currents. For all nonhermetic devices failure occurred as a result of a large increase in the threshold current. The reverse leakage current for the failures did not increase when the threshold current increased, indicating that the change in threshold was a result of a change in reflectivity of one or both facets. The hermetic control group of devices aged under many of the same conditions showed a gradual increase in both the threshold current and slope efficiency. The median lifetimes as determined by assuming a device was a failure when the threshold current increased by 50% was strongly dependent upon humidity temperature and drive current. The lifetime data was fit to and equation of the form lifetime exp(-E/sub /spl alpha///kT) exp(-B/sub RH/[RH/sup 2/]). The values of E/sub /spl alpha// and B/sub RH/ were 0.52 eV and 4.9/spl times/10/sup -4//%/sup 2/, respectively. The current drive data was fit to and expression of the form lifetime a exp(I/sup /spl alpha//I/sub op/) where I/sub /spl alpha// as 0.09 h/mA. The lifetime dependence on current drive was modeled by assuming that the drive current caused a local temperature rise through thermal resistance. This local temperature rise then caused a decrease in the local humidity at the diode surface through an expression of the form %RH/sub diode//spl alpha/ exp (-5990[1/(T/sub r/+T/sub ambient/)-1/T/sub ambient/])where where T/sub r/ is the local temperature rise due to thermal impedance. Finally, we present our preliminary results on the reliability of nonhermetic SiO/sub x/ passivated lasers. These results indicate that such lasers can be made with sufficient reliability for use in telecommunications application.