1. Optical Design
Concepts
TELECOM BASICS

2. 2
Optical Transmission Path

3. 3
Attenuation

4. 4
Dispersion in SMF
Typical nominal values of 3.5 ps/nm.km for 1300nm and
18 ps/nm. km for 1550nm fibre cables, and are the values are
used as default in optical budget
calculations.

5. 5
Types of Fibre

6. 6
Application Code
 In the format; S-1.1,
 I (Intra office) -1 (STM-1) .1 (1300nm on G652 Fibre)
 S (Short Haul) - 4 (STM-4) .2 (1550nm on G652/653/654)
 L (Long Haul) - 16 (STM-16).3 (1550nm on G653 Fibre)
 I is for use in building. Low power.
 S is less than receiver sensitivity. Generally less than -8dBm. No
attenuation required
 L is higher receiver sensitivity. Generally about -0dBm. Attenuation (fibre)
required

7. 7
Typical Optical Path

8. 8
Optical Parameters
Unit Values
DIGITAL SIGNAL
Nominal bit rate
kbit/s STM-4 according to G.707 and G.958
622 080
Application code
(Table 1/G.957)
S-4.1 L-4.1 L-4.2 L-4.3
(2)
BER
(1)
1x10-10 1x10-10
1x10-10
1x10-10
Operating wavelength range nm 1274/1356 1296/1335 1480/1580 1480/1580
TRANSMITTER AT REFERENCE POINT MPI-S
Source type MLM MLM/SLM SLM
Spectral characteristics
- maximum RMS width (σ) nm 2.5 1.7 / - - -
- maximum -20dB width nm - - / 1 <1 1
- minimum SMSR dB - - / 30 30 30
Mean launched power
- maximum dBm -8 2 2 2
- minimum dBm -15 -3 -3 -3
Minimum extinction ratio dB 8.2 10 10 10
OPTICAL PATH BETWEEN MPI-S AND MPI-R
Attenuation range dB 0÷12 10÷24 10÷24 10÷24
Maximum dispersion ps/nm 74 NA 1600 NA
Minimum ORL of cable plant at MPI-S dB NA 20 24 20
Maximum discrete reflectance between MPI-S and MPI-R dB NA -25 -27 -25
RECEIVER AT REFERENCE POINT MPI-R
Receiver type PIN PIN PIN
Minimum sensitivity
(1) dBm -28 -28 -28 -28
Minimum overload dBm -8 -8 -8 -8
Maximum optical path penalty dB 1 1 1 1
Maximum reflectance of receiver, measured at MPI-R dB NA -14 -27 -14

9. 9
Calculation
 L4.1
 This typical calculation is based on the parameter values for the synchronous multiplexer
 From L4.1 table. Min Sens. = -28dBm. Min Launch = -3dB. Path Penalty = 1dB.
Assume 3dB of splice loss.
 coefficient is 0.34 dB/Km.
 Dispersion = N/A (3.5ps/nm/km)
 -28 + 3 + 1 + 3 = 21dBm : 21 / 0.34 = 61.7km
 L4.2
 This typical calculation is based on the parameter values for the synchronous multiplexer
 From L4.2 table. Min Sens. = -28dBm. Min Launch = -3dB. Path Penalty = 1dB.
Assume 3dB of splice loss.
 coefficient is 0.2dB/Km.
 Dispersion = 1600ps/nm (18ps/nm/km)
 -28 + 3 + 1 + 3 = 21dBm : 21 / 0.2 = 105km (attenuation limited)
 1600 / 18 = 88.8km (dispersion limited)

10. 10
Single Fibre Working
 STM1 1310/1310nm
 STM1 1310/1550nm
 STM1 RED/BLUE 1536/1554nm
TX
RX
RX
TX
Single Fibre
Couplers

11. 11
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