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.
Evolution of optical subassemblies in IBM data communication transceivers
Optical subassemblies (OSAs) are the highest-cost component of datacom transceivers, and therefore the component that is most constrained by production cost concerns. While transceiver costs have declined, operating rates have increased from 266 Mb/s to 10.3 Gb/s. Corresponding OSA designs, based on multimode fiber, have evolved incrementally through several generations, to 2.4 Gb/s. Costs have been lowered in successive generations by reducing the number of parts, material costs, and complexity of assembly, and by using lower-cost optoelectronic devices--vertical-cavity surface-emitting lasers (VCSELs). This paper traces the mechanical aspects of OSAs that have been developed and introduced into products or developed as demonstration projects.
Hewlett Packard singlemode Small Form Factor (SFF) module incorporates micromachined silicon, automated passive alignment, and non-hermetic packaging to enable the next generation of low-cost fibre optic transceivers
Hewlett Packard (HP) is currently manufacturing a range of multimode and singlemode (SM) SFF transceivers with data rates from 125 Mb/s to 1.25 Gb/s (higher data rates are being developed). This paper addresses the singlemode module design, assembly techniques and performance. HP SFF transceivers offer the same functionality as SC duplex transceivers but utilise the mini MT-RJ optical interface in order to achieve twice the port density. HP SFF modules are price competitive with SC duplex modules, and are designed to enable low cost, high volume manufacture. In order to meet the size constraints and achieve low manufacturing costs, the HP SM SFF transceiver utilises silicon as a base to support the optical fibres and active components, and as an aid to passively align of the active components to the fibres. Most other passively aligned modules require the use of a more expensive expanded mode region laser diode (LD). But HP has developed a unique passive align and attach system that can easily achieve the required coupling power for Fast Ethernet, OC3 and Gigabit Ethernet using a standard 1300 nm strained MQW LD. The module design and the methods used for passive align are discussed, as is the precision die attach (PDA) equipment. All previous HP SM modules relied on an hermetic cavity around the active devices to achieve the reliability assurance, e.g. as defined in Bellcore TA-NWT-000983, but this type of hermetic design has limited potential for cost reduction. The HP SM SFF module is designed to meet the same assurance levels, but uses silicone encapsulation in place of hermeticity, and the results of the qualification testing are presented.