Itu-t rec. G. 957 (06/99) Optical interfaces for equipments and systems relating to the synchronous digital hierarchy

Table B.1/G.957 – Nominal values of attenuation and group delay distortion

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T-REC-G.957-199907-S!!PDF-E
co so truyen thong soi quang chuong 3 bo phat quang

Figure B.2/G.957 – Low-pass receiver filter for measuring the transmitter eye diagram
Table B.2/G.957 – Tolerance values of the attenuation of the optical reference receiver ∆ a (dB) a) f/f

Table B.1/G.957 – Nominal values of attenuation and group delay distortion
of the optical reference receiver
f/f
0

f/f
r

Attenuation (dB)
Group delay distortion (UI)
0.15 0.2
0.1
0
0.3 0.4
0.4
0
0.45 0.6
1.0
0
0.6 0.8
1.9
0.002
0.75 1.0
3.0
0.008
0.9 1.2
4.5
0.025
1.0 1.33
5.7
0.044
1.05 1.4
6.4
0.055
1.2 1.6
8.5
0.10
1.35 1.8
10.9
0.14
1.5 2.0
13.4
0.19
2.0 2.67
21.5
0.30
U
0
T1509040-92
R
R
H p
U
0
U
2
( )
=
2
U
2
Low-pass filter
Figure B.2/G.957 – Low-pass receiver filter for measuring the transmitter eye diagram

Recommendation G.957 (06/99)
22
To allow for tolerances of the optical reference receiver components including the low-pass filter, the
actual attenuation should not deviate from the nominal attenuation by more than the values specified
in Table B.2. The flatness of the group delay should be checked in the frequency band below the
reference frequency. The tolerable deviation is for further study.
Table B.2/G.957 – Tolerance values of the attenuation of the optical reference receiver
∆

a (dB)
a)

f/f
r

STM-1 STM-4 STM-16

0.001 .. 1
±
0.3
±
0.3
±
0.5
1 .. 2
±
0.3
…
±
2.0
±
0.3
…
±
2.0
±
0.5
…
±
3.0
a)
Provisional values.
NOTE – Intermediate values of
∆
a should be interpolated linearly on a
logarithmic frequency scale.
APPENDIX I

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