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.

Control subsystem

The control subsystem implements the SEMF (Synchronous Device Management Function) defined in G.783, communicates with external management systems through the standard QB3 CMIP interface, and the management information model complies with the ITU-T G.774 series recommendations. Adopting a two-level centralized control architecture:

Equipment Controller (EC): responsible for DCC networking, CT/OS interface, database management, and can manage up to 32 DCC channels;

Rack Controller (SC): located in the SDH matrix unit, responsible for configuration issuance, alarm detection, performance monitoring, and equipment protection switching.

The two communicate through the internal serial bus (ISSB) of the rack. The PCMCIA flash card on EC provides massive storage for configuration databases and software packages. EC also supports intermediary device functionality, which can manage other Alcatel devices (such as access multiplexers, microwave systems, PDH terminals) that share the same address through Q2/RQ2 interfaces, and transmit management information to TMN through SDH DCC without deploying additional data communication networks. When the matrix 1+1 protection is applied, the rack controller function is also protected synchronously - EC failure does not affect business or automatic protection switching.

Business Port Subsystem

1660SM provides a wide range of SDH/PDH service port cards, covering all speeds from 2M to 10G:

Main characteristics of board types

63 × 2Mb/s asynchronous mapping to VC12, supporting 75 Ω/120 Ω, up to 6+1 blocks

3 × 34/45Mb/s software switchable, asynchronously mapped to VC3, up to 16 blocks

4 × OC3 (AU3/TU3 conversion) supports SONET OC-3 streams to achieve AU3 ↔ TU3 conversion enables the transmission of SONET VC3 in SDH networks

4 × 140Mb/s/STM-1 software switchable per port, VC4 can be unstructured or low order structured

4 × STM-1 electric/optical multiple short/long distance combinations, arbitrary mixing and plugging

1 × STM-4 optical short/long distance, up to 16 pieces

4 x STM-1/4 optical (SFP) supports SFP modules and can be expanded with 12 x STM-1 optical access modules

16 × STM-1 electrical access combined with 4 × STM-1/4 main ports for use

1 x STM-16 optical short/long/color version (directly connected to DWDM), up to 4 pieces

Up to 16 pieces of 1 × STM-16 Slim Fiber Optic (SFP)

1 x STM-64 optical single port 10G, supports S-64.2b/I-64.1/L-64.2b (with 10dB optical amplifier), can carry 64 x VC4, 16 x VC4-4c, 4 x VC4-16c or 1 x VC4-64c. High order processing of 64 AU4, of which 32 AU4 can be low order structured. Up to 4 yuan

STM-64 is a key new capability of Release 5, enabling 1660SM to directly connect to 10G backbone rings.

ISA Data Service Adaptation - The Core of Next Generation SDH

The ISA (Integrated Service Adapter) module enables 1660SM to evolve from a traditional TDM device to a multi service fusion platform, enabling native processing of data traffic.

6.1 ISA Ethernet 10/100 BaseT

The main card provides 11 10/100BaseT interfaces, and the access module provides 14 additional interfaces (or 2 1000BaseSX/LX SFPs through a 4xGbE access module);

Each Ethernet interface can be independently mapped to VC12/VC3/VC4, or cascaded to N × VC12/VC3;

Encapsulated with GFP (Generic Framing Protocol) and using 802.3x flow control to prevent congestion;

Speed adaptation can flexibly adjust bandwidth according to customer needs;

Up to 12 main cards and 12 access modules.

6.2 ISA Gigabit Ethernet (GigE)

Provide 4 1000BaseSX/LX SFP interfaces;

Carrying GigE traffic through virtual cascading (VC-4-xv, x=1-7), in compliance with G.707/G.783 and LCAS (G.7042);

Enhanced slot backplane throughput of 1.2Gb/s, non enhanced slot throughput of 622Mb/s;

Up to 8 cards (32 GbE interfaces).

6.3 ISA Packet Ring Edge Aggregator (PREA)

1.6Gbps switching capability, integrated L2 functionality and MPLS based backbone connectivity;

Two models: 4 × 10/100BaseT or 1 × 1000BaseX;

Multiple ISA Ethernet cards can be converged and transmitted through SDH to a single virtual container or VC-x packet cascade bundling.

6.4 ISA ATM Card Insertion

600Mbps (1 slot) or 1200Mbps (2 slots), Enhanced version supports up to 252 E1 internal interfaces (for UMTS IMA applications);

Support both hard PVC and soft PVC (PNNI signaling);

Traffic types: UBR, UBR+, CBR, VBR rt/nrt, GFR.2;

Congestion avoidance: selective cell dropout (SCD)+early/late packet dropout (EPD/TPD);

Up to 4 pieces, supporting 1+1 protection groups.

6.5 Ethernet Switch (ES1/ES4/ES16)

Introduce L2 switching capability within the SDH platform;

ES16 (2.5Gbps) supports MPLS Martini encapsulation and classification based on port, 802.1Q, MAC address, MPLS label, and IP-TOS/DSCP;

Support SLA (guaranteed and best effort) defined by CIR/PIR;

Up to 8 ES modules.

6.6 ISA Packet Ring

6.4Gbps switching capacity (2 slots wide), based on Ethernet over MPLS technology;

Support VPWS (Virtual Dedicated Line) and VPLS (Virtual Private Network) services;

Support three SLA attributes: guarantee, adjustment, and best effort;

Global congestion avoidance control for the entire network, providing statistical reuse for best effort service bursts.

Integrated Coarse Wavelength Division Multiplexing (CWDM)

1660SM directly integrates CWDM function, enabling multi wavelength transmission without the need for external devices:

STM-16 color port: compliant with ITU-T G.694.2 grid (1470~1610nm, 8 wavelengths), wavelength selected through SFP transceiver;

OADM module: 1-channel or 2-channel add/drop multiplexing;

8-channel AUX/DEMUX module: full grid add/drop;

Dual multi rate repeater: supports black/white ↔ Color conversion and color ↔ Color reproduction, client signals support FDDI, Fast Ethernet, STM-1/4/16, ESCON, Fiber Channel, GigE, 2xGigE, STM-16 with FEC, etc;

4 × ANY board: Reuse up to 4 customer signals (Fast Ethernet, FDDI, ESCON, Digital Video, Fiber Channel, FICON, GigE) into a single 2.5Gb/s optical channel (server signal).

Auxiliary expenses and network management

1660SM fully supports the management of SDH segment overhead and channel overhead bytes (see Table 3-6 for details), including A1/A2, J0, B1, E1, D1-D3 for RSOH, B2, K1/K2, D4-D12, S1 (SSM), M1, E2 for MSOH, as well as J1, B3, C2, G1, F2/F3, H4 for VC4/VC3, and V5, J2 for VC12.

In addition, provide:

TCM (serial connection monitoring) capability, supporting monitoring within the operator's domain;

4 x V.11, 4 x RS-232, 4 x G.703 (64kb/s), 2 x G.703 (2Mb/s) auxiliary terminals;

Support optical amplifier (enhanced type, 2 slot width) MUX/DEMUX、OADM。

Overview of Network Protection Mechanisms

Characteristics of Applicable Scenarios for Protection Types

Linear MSP point-to-point link 1+1/1: N, single ended or double ended

MS-SPRing STM-16/64 ring network, 2 fiber bidirectional, up to 2 rings (STM-64 level)

SNCP/I (intrinsic) any topology subnet connection protection, all VC levels

SNCP/N (non-invasive) interference free monitoring and protection for any topology

Equipment redundancy node level matrix 1+1, EC redundancy, power distribution redundancy