Tegal Corp. announced it has completed the sale of a 901g plasma etch system to a California-based telecommunications company for the production of optical networking technologies. The etcher is expected to be installed in the customer's Northern California facility by the end of this month.   . . .   Former JDS Uniphase executive Ian Croston has been appointed director of engineering at Glasgow, Scotland-based Essient Photonics, a supplier of integrated III-V optoelectronic components for modulation and detection in 10 Gb/s and 40 G/ps systems. Essient recently received $7 million in initial funding.