Alcatel Lucent 1660SM Optical Transmission System Architecture and Business Bearer

Alcatel Lucent 1660SM Optical Transmission System Architecture and Business Bearer

SDH (Synchronous Digital Hierarchy) remains the dominant transmission technology in metropolitan and regional networks to this day. With the continuous growth of high-speed data communication demand, Alcatel Lucent has enhanced data sensing capabilities in its leading optical transmission equipment portfolio - aggregating, switching, and forwarding traffic at appropriate data layers - to provide high-performance multi technology network solutions. Alcatel 1660SM (belonging to the OMSN Optical Multi Service Nodes product family) is the culmination of this concept. Equipped with ISA (Integrated Service Adapter) plug and play module, it achieves efficient aggregation of multi protocol broadband services such as Ethernet, MPLS, ATM, and packet ring, providing a powerful integrated platform for telecom operators and service providers to build intelligent optical networks.

Product positioning and strategic value

1660SM complies with the SDH standard defined by ITU-T G.707. Release 5 enhances the capabilities of the installed equipment by adding STM-64 interfaces and expanding the switching capacity through a new matrix module. It can be flexibly configured as a multi line terminal multiplexer, add/drop multiplexer, or small cross connect device, suitable for linear links, ring networks, and mesh networks, and provides multiple network protection mechanisms in all applications.

Core advantages

Flexibility: With very few shared components, the 1660SM has 16 dedicated business port slots, making it highly flexible. The system can be configured as an STM-64 ring network node, capable of terminating up to 6 STM-16 rings, supporting multiple SNCP rings or two 2F MS-SPRrings.

Reliability: Provides three types of network protection - linear multiplexing segment protection (MSP), bidirectional shared ring protection (MS SPRing), and subnet connection protection (SNCP). All replaceable units can be optionally redundant, and power protection is naturally implemented by distributed DC/DC conversion of each board.

Simplicity: Centralized control architecture, with processors and software limited to device controllers, matrix units, and ATM/ISA packet switching cards. Business ports have no onboard processors, significantly reducing maintenance complexity.

Openness: Supports direct communication between "colored" STM-16 interfaces and WDM devices without the need for intermediate wavelength adapters, supports AU4 cascading to interface with high throughput ATM/IP devices, and can achieve SDH/SONET conversion.

Hardware architecture and cross connection core

2.1 Chassis Structure

The 1660SM main frame adopts a 19 inch ETSI compatible chassis (482mm wide x 650mm high x 250mm deep), divided into an upper access area and a lower business control area:

Access area (21 slots): accommodates synchronous I/O modules, power and alarm interfaces, 18 business access module slots, supports 2M/34M/45M/140M/STM-1 electrical ports, 16 × STM-1 electrical ports, 12 × STM-1 optical ports, 14 × 10/100 Ethernet, 4 × GbE and other access modules.

Lower part (20 slots): 2 matrix board slots, 1 device controller slot, 16 business card slots, supporting 63 × 2M, 3 × 34/45M, 4 × 140/STM-1, various STM-1/4/16/64 optical interfaces, and ISA series data cards.

2.2 SDH Cross Connection Subsystem

The 1660SM SDH cross connection is based on a non blocking matrix and can interconnect AU4, TU3, and TU12 between any SDH or PDH port. Supports multiple connection types:

Unidirectional point-to-point, bidirectional point-to-point, unidirectional point-to-point to multipoint;

SNCP Drop & Continue；

MS-SPRing Drop & Continue。

Matrix capacity:

High level VC layer: 384 × 384 STM-1 equivalent (i.e. 384 VC4);

Low order VC layer: 256 × 256 STM-1 equivalent (i.e. 16128 VC12).

All AUGs are structured according to the standard ETSI mapping (1 × AU4). Matrix support:

Single ended SNCP/N (non-invasive) and SNCP/I (intrinsic);

MS SPRing protection (recoverable or non recoverable mode);

Maximum 2 × 2 fiber MS SPRing protection (STM-64 level, including 96 STM-1 branches);

The matrix can be configured with 1+1 protection.

The cascaded signals of AU4-4C, AU4-16C, and AU4-64C can be cross connected between any STM-4/16/64 port.

Clock Synchronization Subsystem (SETS)

The synchronization subsystem provides all timing references required by network elements, representing the SDH Equipment Clock (SEC), in accordance with the SETS (SDH Equipment Timing Source) functional definition of ITU-T G.783.

3.1 Input Source

You can choose synchronous input from the following sources:

STM-n line;

2Mb/s business port;

2MHz/2Mb/s external input;

Internal oscillator.

Automatic selection through SSM (Synchronous State Message) quality algorithm or priority criteria, and manual selection is also supported.

3.2 Output and Mode

Generate two outputs: one serves as an internal timing source and synchronously outputs SDH STM-n signals; Two external 2MHz or 2Mb/s outputs are provided for use by external devices. Up to 6 candidate reference sources can be selected (from all STM-n and 2Mb/s ports). SETG (Synchronous Device Timing Generator) has three working modes: lock, hold, and free oscillation. In hold mode, the maximum drift is 0.37ppm/day, and the local oscillator accuracy is 4.6ppm. When the matrix 1+1 is protected, the clock reference function is also protected.