M320 Attenuation In Sonet/Sdh Pics; Calculating Power Budget For Fiber-Optic Cable For M Series, Mx Series, And T Series Routers; Appendix E M320 Router Cable And Wire Guidelines And Specifications - Juniper M320 Hardware Manual

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M320 Attenuation in SONET/SDH PICs

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Calculating Power Budget for Fiber-Optic Cable for M Series, MX Series, and T Series Routers

Copyright © 2010, Juniper Networks, Inc.
document GR-253-CORE (Section 4.3) and International Telecommunications Union
(ITU) document G.957.
When chromatic dispersion is at the maximum allowed, its effect can be considered as
a power penalty in the power budget. The optical power budget must allow for the sum
of component attenuation, power penalties (including those from dispersion), and a
safety margin for unexpected losses.
Calculating Power Budget for Fiber-Optic Cable for M Series, MX Series, and T Series
Routers on page 261
Calculating Power Margin for Fiber-Optic Cable for M Series, MX Series, and T Series
Routers on page 262
M320 Routing Engine Interface Cable and Wire Specifications on page 264
SONET/SDH transceivers in the different reach classes—such as short reach (SR),
intermediate reach (IR), or long reach (LR)—generate different output power levels and
tolerate different input power levels. Transceivers that have a longer reach can transmit
enough power to saturate the receivers on PICs that have a shorter reach. Specifically,
LR transceivers can saturate IR PICs, and both IR and LR transceivers can saturate SR
PICs. Transceivers in the same reach class can also saturate one another.
To prevent saturation, you might need to attenuate power at the PIC receiver, particularly
if you know that it has a shorter reach than the transceiver that is sending the signal.
Determine the amount of attenuation needed by measuring the power level at each
receiver. Attenuate the power to bring it within the allowable range; for short lengths of
fiber, with fiber and connector loss close to zero, an attenuator of 5 to 10 dB should be
sufficient.
For specifications of minimum and maximum input level (receiver sensitivity and receiver
saturation) and minimum and maximum output level (average launch power) for the
SONET/SDH PICs supported on the M320 router, see the M320 Multiservice Edge Router
PIC Guide.
M320 Power System Description on page 33
M320 Site Preparation Checklist Requirements on page 41
General Electrical Safety Warnings for M Series, MX Series, and T Series Routers on
page 231
Site Electrical Wiring Guidelines for M Series, MX Series, and T Series Routers on page 249
To ensure that fiber-optic connections have sufficient power for correct operation, you
need to calculate the link's power budget, which is the maximum amount of power it
can transmit. When you calculate the power budget, you use a worst-case analysis to
provide a margin of error, even though all the parts of an actual system do not operate
Appendix E: M320 Router Cable and Wire Guidelines and Specifications
261