With a view to expanding its transponder line and further developing systems that integrate optics, electronics and hard- and software, Avanex Corp. of Fremont, Calif., is acquiring certain assets of the Optical Systems Div. of Vitesse Semiconductor Corp. in San Jose, Calif., for approximately 1.2 million shares of its common stock. Under the agreement, Avanex, a supplier of photonic processing subsystems for the optic layer in telecommunications networks, also will purchase up to $2 million in products over the next three years from Vitesse, which produces high-speed communication integrated circuits. Completion of the transaction, valued at approximately $6 million, is subject to routine closing procedures.