The Positron OSIRIS multi-service Platform (MSP) is an integrated access solution for the rapidly expanding synchronous optical network (SONET) broadband markets. It delivers the most cost-effective, compact and simple-to-deploy solution for multiservice traffic such as data, voice and video.

The Optical Access Unit (OAU) provides the multiplexing and demultiplexing for all mapper units in SONET networks. It also provides electrical-to-optical conversion of the associated signals. The OC-3 OAU collects all payload data from the backplane and adds the SONET framing and overhead to build the standard STS-1 signal.

OC-3 OAU Technology

The OSIRIS STD Shelf comes with a pre-installed alarm and craft interface unit (ACIU) in the leftmost slot and a tributary interface unit (TIU) in the rightmost slot. Both of these cards can be ordered separately as replacements.

The OC-3 OAU performs all necessary synchronization, pointer and overhead processing. To provide traffic protection, two OAUs can be installed. One OAU, installed in the OAU-A slot, provides the optical interface to the working ring. The other OAU, installed in the OAU-B slot, provides the optical interface to the protection ring.

The OC-3 OAU is available in intermediate-reach and long-reach versions. The OAUs require a buffer interface unit (BIU) when installed in an OSIRIS XTD Shelf or in an OSIRIS XTS Shelf. The BIUs are installed in the BIU slots. The OAUs have two connectors for input/output connection to fiber patch cords. ST, SC and FC connectors are available.


  • Capability to achieve wide-range distances and operate in a multi-vendor network
  • Cost-effective and compact units
  • Easy in-service capacity upgrade
  • Multi-ring interconnection capability
  • No requirement for external synchronization modules
  • Robust SONET-based protection


  • Various optical budgets and wavelengths available
  • One-step multiplexing allowing time slot assignment
  • Single OAU faces both east and west directions in a ring
  • Drop-and-continue support
  • Built-in synchronization circuitry
  • Full support of unidirectional path switched ring (UPSR) protection
  • Capability to interoperate with other SONET equipment
  • Support for concatenated traffic (STS-3c)