Opnext Inc is a very major supplier of Optical Transceivers to most (if not all) key Telecomms and Datacomms equipment manufacturers. Spawned from Optical Components groups within Hitachi, Japan Opnext  is vertically integrated, manufacturing the key Optical semiconductors as well as the fulltransceivers. Its range covers SFP and goes via 10G XFP X2 Xenpak right up to 40G. Highlights are the 300pin tunable 10G Transponders and the 43G client transceivers and the line versions under development.

OE Solutions (S.Korea) was formed out of Samsung. It supplies niche market SFPs for CWDM, BiDi and supervision channel. Its high level of service typifies Korean suppliers.

Licomm was also formed by Samsung staff and it addresses erbium fiber based amplification and instrumentation needs. Active in standard TDM/DWDM EDFAs, Licomm also has special HP EDFA @ 35dBm for analog transmission as well as transient supression designs for ROADM systems.
Licomm is also involved in the Analog Rx and Fttx (G-PON and GE-PON) technology and provides  Instrumnentation for such applications.

Based in Daejon, S Korea, East Photonics' key business and value proposition is to manufacture Optical passive components in fused fibre, TFF and PLC technologies  to a consistently high level of  build which is needed in the passive optical business. Quick response to custom needs and short leadtimes can be expected from EP.

SOA amplification technologies are the core of Alphion's business. The core comes from ex-Bell labs staff who havehoned the product and have real value propositions in the use of comms band SOAs in contemporary PON and FttX extension. The worth will really come to light in the deployment @ 10G. 
Alphions products are also finding traction in FO sensor interrogators, a marked application being in Optical Computer Tomography.

Kyosemi is a small but reactive Japanese company formed from Inductry professionals with much background in Optoelectronic semiconductors. Specialising in PD technology in Si and InGaAs, Kyosemi addresses many niche markets such as UV & IR sensing for instrumentation as well as having innovatibe designs for Solar cells.