and ATM Self-Healing Ring
The single-mode fiber network for the SONET OC-192
testbed in Austin Texas was deployed in the spring of 1996. The three nodes are located at the Southwestern
Bell TRI Lab, ARL (Applied Research Lab, University of Texas), and the Electrical and Computer Engineering
(ECE) Department, University of Texas (UT). The fiber distance between the nodes is approximately 22,
35 and 33 km respectively, routed through several Southwestern Bell central offices. The total ring
length is 90 km.
In April 1996, Bellcore staff members travelled
to Austin to perform the fiber plant field tests with the assistance of SBC-TRI staff. The overall test
results show the fiber plant to be in excellent condition with low loss and low reflections throughout.
From the OTDR measurement, all fiber links have a loss of about 0.31 dB/km (including jumper losses)
in the 1550 nm spectral region, and the return loss of connectors/splices are typically better than
40 dB, except for the ARL node which has a return loss of 33 dB. It was found that the fiber plant can
support OC-192 traffic with a sensitivity penalty of < 1 dB. The fiber plant is therefore ready for
the SONET OC-192 testbed system deployment.
The design and fabrication of two 9.953 Gb/s
SONET multiplexing, framing, and phase-aligner integrated circuits (ICs) using the Heterojunction Bipolar
Technology (HBT) of Rockwell International has been completed. Bellcore, working closely with Rockwell
International, has demonstrated the feasibility of implementing byte multiplexing at the SONET OC-192
level by prototyping experimentally a 1:8 demultiplexer/framer IC and and an 8:1 multiplexer/phase aligner
IC, which together form the high-speed interfaces of a SONET STS-192 add-drop multiplexer (ADM). In
addition, Bellcore has completed the design and packaging of two high-speed modules for the ICs so as
to provide a turnkey interface between the intermediate speed electronics and the 10 Gb/s optical subsystems
of a SONET OC-192 add-drop multiplexer.
Tektronix has completed the fabrication and initial
testing of its SONET OC-192 receiver and transmitter cards that use the Bellcore supplied high-speed
modules. Six of these OC-192 cards will be used in conjunction with additional Tektronix supplied OC-48
cards to form the add-drop multiplexers at the three nodes of the Austin testbed. In addition, Tektronix
intends to leverage the development of the OC-192 cards for its commercial video and SONET test equipment
requirements.
Lucent Technologies has completed fabrication
of a new Phase II microprocessor controlled 10 Gb/s 1550nm optical receiver/transmitter pair that is
both manufacturable and of compact size. The new optics are about one-fourth the size of their phase
I counterparts, consume a fraction of the power of the previous design, and maintain the previous design's
excellent receiver sensitivity and eye margin. Five of these phase II transmitter/receiver pairs will
be installed in the Austin testbed this fall. This work will also support Lucent's overall commercial
SONET OC-192 development efforts.
Washington University in St. Louis is nearing
completion of a set of three chips and associated hardware and software that implements a uniquely scalable
and flexible ATM switch supporting link speeds from 150 Mb/s to 2.4 Gb/s and capable of supporting configurations
with total throughputs from 10 Gb/s to more than 10 Tb/s. Washington University is actively seeking
collaborations or partnerships to make this technology more widely available. This includes relationships
with commercial organizations interested in producing and selling high performance ATM switching systems
using this technology.
Bellcore, working closely with Washington University, has designed and implemented an OC-12c interface for the Washington University gigabit ATM switch. This has been implemented as an OC-12c line card that plugs into the main switch board, interfacing to a pair of custom port processor chips designed to perform ATM cell processing (including VCI translation, cell buffering, rate and format conversions, maintenance and control functions). The port processors have been designed to support a variety of transmission interfaces including SONET OC-3c, OC-12c and OC-48c, as well as transmission interfaces using single and dual Hewlett Packard G-link transmission chips. One of the key technical challenges was to identify an interface specification that could accommodate such a variety of interfaces without unduly complicating the framer circuitry in the ATM port processors.
Bellcore and Tektronix together have completed
a product analysis methodology report for SONET OC-192. The document is a comprehensive list of tests
and test methodologies needed to verify the compliance of SONET OC-192 equipment with Bellcore's GR-1377
SONET OC-192 generic requirements standards. In addition, extensive internal work at Bellcore has focused
on SONET OC-192 product analysis methodology in preparation for the launch of Bellcore's commercial
OC-192 compliance analysis services through Bellcore's Professional Services organization.