Recommendation G.957 (06/99)
6
Table 3/G.957 – Parameters specified for STM-4 optical interfaces
Unit
Values
Digital signal
Nominal bit rate
kbit/s
STM-4 according to Recommendation G.707
622 080
Application code (Table 1)
I-4
S-4.1
S-4.2
L-4.1
L-4.2
L-4.3
Operating wavelength range
nm
1261
a)
-1360
1293-1334/
1274-1356
1430-1580
1300-1325/
1296-1330
1280-1335 1480-1580 1480-1580
Transmitter at reference point S
Source
type
MLM LED MLM SLM MLM SLM SLM SLM
Spectral
characteristics:
– maximum RMS width (
σ
)
nm 14.5
35 4/2.5
– 2.0/1.7 –
–
–
– maximum –20 dB width
nm
–
–
– 1 – 1
< 1
b)
1
– minimum side mode suppression ratio
dB
–
–
– 30 – 30 30 30
Mean
launched
power:
– maximum
dBm
−
8
−
8
−
8
+
2
+
2
+
2
– minimum
dBm
−
15
−
15
−
15
−
3
−
3
−
3
Minimum extinction ratio
dB
8.2
8.2
8.2
10
10
10
Optical path between S and R
Attenuation range
c)
dB 0-7 0-12
0-12 10-24 10-24
10-24
Maximum dispersion
ps/nm
13
14
46/74
NA
92/109
NA
b)
NA
Minimum optical return loss of cable plant at S,
including
any connectors
dB
NA NA
24 20 24
20
Maximum discrete reflectance between S and R
dB
NA
NA
−
27
−
25
−
27
−
25
Receiver at reference point R
Minimum sensitivity
c)
dBm
−
23
−
28
−
28
−
28
−
28
−
28
Minimum overload
dBm
−
8
−
8
−
8
−
8
−
8
−
8
Maximum optical path penalty
dB
1
1
1
1
1
1
Maximum reflectance of receiver, measured at R
dB
NA
NA
−
27
−
14
−
27
−
14
a)
Some Administrations may require a limit of 1270 nm.
b)
See
6.2.2
c)
See clause 6.
Recommendation G.957 (06/99)
7
Table 4/G.957 – Parameters specified for STM-16 optical interfaces
Unit
Values
Digital signal
Nominal bit rate
kbit/s
STM-16 according to Recommendation G.707
2 488 320
Application code (Table 1)
I-16
S-16.1
S-16.2
L-16.1
L-16.2
L-16.3
Operating wavelength range
nm 1266
a)
-1360 1260
a)
-1360 1430-1580 1280-1335 1500-1580 1500-1580
Transmitter at reference
point S
Source type
MLM
SLM
SLM
SLM
SLM
SLM
Spectral characteristics:
– maximum RMS width (
σ
)
nm 4
–
–
–
–
–
– maximum –20 dB width
nm
– 1
<
1
b)
1
<
1
b)
<
1
b)
– minimum side mode
– suppression ratio
dB
– 30 30
30 30 30
Mean launched power:
– maximum
dBm
−
3
0 0
+
3
+
3
+
3
– minimum
dBm
−
10
−
5
−
5
−
2
−
2
−
2
Minimum extinction ratio
dB
8.2
8.2
8.2
8.2
8.2
8.2
Optical path between S and R
Attenuation range
c)
dB 0-7
0-12 0-12 10-24
e)
10-24
e)
10-24
e)
Maximum dispersion
ps/nm
12
NA
b)
NA
1200-1600
b)
,
d)
b)
Minimum optical return loss
of cable plant at S, including
any connectors
dB 24
24
24
24
24
24
Maximum discrete reflectance
between S and R
dB
−
27
−
27
−
27
−
27
−
27
−
27
Receiver at reference point R
Minimum sensitivity
c)
dBm
−
18
−
18
−
18
−
27
−
28
−
27
Minimum overload
dBm
−
3
0 0
−
9
−
9
−
9
Maximum optical path penalty
dB
1
1
1
1
2
1
Maximum reflectance of
receiver, measured at R
dB
−
27
−
27
−
27
−
27
−
27
−
27
a)
Some Administrations may require a limit of 1270 nm.
b)
See 6.2.2.
c)
See clause 6.
d)
The indicated dispersion range corresponds to the approximate worst-case dispersion for 80 km G.652/G.654 fibre
over the wavelength range 1500-1580 nm: manufacturers shall ensure sufficient margins to guarantee proper
operation over a target distance of 80 km.
e)
To meet 10 dB minimum attenuation instead of 12 dB, it will be required to decrease
the maximum output
power, to increase the minimum overload, to use optical attenuators, or a combination thereof.
Recommendation G.957 (06/99)
8
6 Parameter
definitions
For the purposes of this Recommendation, optical fibre line system interfaces can be represented as
shown in Figure 1. In Figure 1, point S is a reference point on the optical fibre just after the
transmitter optical connector (C
TX
) and point R is a reference point on the optical fibre just before
the receiver optical connector (C
RX
). Additional connectors at a distribution frame (if used) are
considered to be part of the fibre link and to be located between points S and R. In this
Recommendation, optical parameters are specified for the transmitter at point S,
for the receiver at
point R, and for the optical path between points S and R.
T1508970-92
S
R
C
TX
C
RX
Transmitter
connector
Transmitter
circuit
package
Plant fibre
Receiver
circuit
package
Receiver
connector
Plug
Plug
Figure 1/G.957 – Representation of optical line system interface
All parameter values specified are worst-case values, assumed to be met over the range of standard
operating conditions (i.e. temperature and humidity ranges), and they include aging effects. These
conditions and effects are for further study. The parameters are specified relative to an optical section
design objective of a Bit Error Ratio (BER) not worse than 1
×
10
−
10
for the extreme case of optical
path attenuation and dispersion conditions in each application of Table 1. For systems with improved
performance (e.g. BER of 10
−
12
or better according to Recommendation G.826), either improved
receiver sensitivity or reduced attenuation range for the applications in Table 1 may be required.
The optical line coding used for all system interfaces is binary Non-Return to Zero (NRZ), scrambled
according to Recommendation G.707.
6.1
System operating wavelength range
To provide flexibility in implementing transversely compatible systems and future usage of
Wavelength-Division Multiplexing (WDM), it is desirable to allow as wide a range as possible for
the system operating wavelengths. The choice of operating wavelength range for each of the
applications of Table 1 depends on several factors including fibre type, source characteristics, system
attenuation range, and dispersion of the optical path. The following general considerations affect the
specification of operating wavelength ranges in this Recommendation. More detailed description of
the system aspects used to develop the operating wavelength range requirements in this
Recommendation is contained in Annex A.