Chapter 18, Dual Optical L4.2 Module, L4.2-2-LC

Dual Optical L4.2 Module, L4.2-2-LC

18.1 Module Description

This is a dual port STM4 module for long haul transmission at 1550nm optical wavelength. The main functions of the module are O/E- E/O conversion and SDH multi-/demultiplexing with VC-12, VC3 and VC-4 granularity. See the "5.1.1 Multiplexing Structure and Mapping Modes" section on page 5-1.

18.1.1 Power Consumption

13W.

18.2 External L-4.2-LC Interface

The 2xL-4.2-LC line interface bitrate is bi-directional with a transmit (Tx) and a receive (Rx) direction. Tx and Rx directions are transmitted on separate fibres. The optical interfaces are compliant to ITU-T Rec. G.957 L-4.2 Long Haul specification for transmission on Single Mode (SM) fibre

18.2.1 Connector Type

The physical connector is a LC connector.

Figure 18-1 STM-4 L4.2-2-LC

Module

18.2.2 Optical Budget

For definitions of optical parameters, see ITU-T Rec. G.957. Reference point S means transmit interface while R is the receive interface.

Table 18-1 Optical Budget - L4.2-2-LC Interface
Parameter	Value
Types of fibre: ITU-T Rec. G.652	10/125	痠
Modulation rate on optical line	622 080	kbit/s
Wavelength range	1480 - 1580	nm
Transmitter at reference point S
Source type	SLM
Spectral characteristics (max. 20 dB width)	1	nm
Mean launched power (max.)	+3	dBm
Mean launched power (min.)	-2	dBm
Min. extinction ratio	10	dB
Optical path between S and R
Attenuation range	10 - 24	dB
Max. tolerable dispersion	3000	ps/nm
Min. optical return loss	24	dB
Max. discrete reflectance between S and R	-27	dB
Receiver at reference point R
Min. sensitivity (BER < 1 in 1010)	-28	dBm
Min. overload	-8	dBm
Max. optical path penalty	1	dB
Max. reflectance at R	-27	dB

18.2.3 Compliance

Table 18-2 .Compliance - L4.2-2-LC Interface
Standard	Comment
ITU-T G.652	Single Mode Fibre specification 10/125
ITU-T G.707	Optical line signal
ITU-T G.813	Optical output jitter
ITU-T G.825	Optical input jitter
ITU-T G.957	Optical spectrum, Optical output power, Optical eye diagram, Optical extinction ratio.

18.2.4 Example of Cable Planning

Table 18-3 Typical Cable Parameters
Cable Loss, according to ITU-T Rec. G.957	Single Mode fibre Acc. to ITU-T G.652
Fibre Cable Attenuation Cable Margin (Mc) Loss in Optical Distribution Frame	0.3 dB/km Incl. in fibre cable attenuation Incl. in fibre cable attenuation


Cable Dispersion:
Maximum Chromatic Dispersion Coefficient	20 ps/nm*km

Table 18-4 Typical Link Spans for 2xL4.2-2-LC
Loss Limited Span	Dispersion Limited Span	Overall Link Span
80 km	150 km	80 km

18.2.4.1 Optical Rx Power Monitoring

The optical input power of the Rx interface is monitored and can be read from the CiscoEdgeCraft terminal.

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