Recommendation G.957 (06/99)
26
However, the test may be applicable in certain cases at the available user ports. It is not proposed as a
general acceptance test which might require special defined access ports and connection
arrangements within the equipment.
APPENDIX III
Possible method for evaluating aging margin contribution
in receiver sensitivity specifications
This appendix presents a possible method for determining the contribution due to aging effects in the
specification of receiver sensitivity used in this Recommendation.
III.1
Receiver sensitivity and eye opening
Figure III.1 shows eye opening at the receiver as a function of optical received power. The eye
opening value, E, is the value which is determined by the system designer for operation at a BER of
10
−
10
. The received power P
2
corresponds to the power required for maximum eye opening at the
receiver. For stable system operation, the optical received power is typically set to a level higher than
P
1
such that, at the end of system life, the specified eye opening, E, is still satisfied. Thus, P
1
is the
end-of-life receiver sensitivity and P
0
is the beginning-of-life receiver sensitivity. M is the margin
between P
1
and P
0
to account for the effects of receiver aging. The amount of eye margin depends on
receiver characteristics and the values, for example, may be E
1
– E and E
2
– E for different receivers
(e.g. type I or type II). An appropriate eye margin cannot be obtained if the received power is P
0
.
With respect to the effects of aging on receiver performance, it may be assumed that the eye opening
as a function of received optical power is shifted parallel to the initial characteristics as shown in
Figure III.2. For the purposes of simulating aging effects, it may also be assumed that the shifted
curve can be obtained by adding a certain amount of intersymbol interference noise to the signal
corresponding to the initial value of eye margin. The test method proposed for evaluation of the eye
opening by this technique is the S/X test.
%
0
E
100
E
2
E
1
P
0
P
1
M
P
2
T1517730-95
End of life
Beginning of life
Eye
opening
Type I
Type II
Received power
Chia sẻ với bạn bè của bạn: |
