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Cisco ONS 15501 User Guide
78-14134-02, Release 2.0
Chapter 1 Product Overview
Cisco ONS 15501 Front Panel
of the add bands. This significantly degrades the OSNR of the pass-through bands, and in cases where
there are more than two EDFAs in the ring, some of the channels in the ring will not meet OSNR
requirements.
To solve this problem, optical power attenuation should be applied on a per channel or per band basis.
More attenuation is typically required for the add bands than for the pass-through bands. At the EDFA
input, the individual channel or band power levels should be equalized as close as possible to the
maximum per channel input power level, (for example, -15 dBm in a 32-channel system). This process
of optical power equalization is necessary to obtain better OSNR.
Inserting attenuation devices such as VOAs (variable optical attenuators) between the OADM (optical
add/drop multiplexer) and the transmitter allows optical power management of individual channels. Per
band power management at the trunk line, between the OADM and the EDFA, is also an effective
method. The Cisco ONS 15501 is capable of supporting either approach, and its wide input range (-29
to 0 dBm) makes it an ideal amplifier for a broad array of ring network designs.
Adding or Dropping Wavelengths
Automatic gain control reacts to the adding or dropping of wavelengths in a network, without requiring
power equalization tuning. The fast response of the Cisco ONS 15501 reduces the impact of adding or
dropping channels, and prevents BER hits.
Adjusting to Span Loss Changes
It is typically necessary to adjust gain and attenuation values both for trunk attenuation and channel or
band power equalization.
Cisco ONS 15501 Front Panel
Figure 1-2 shows the Cisco ONS 15501 front panel. The front panel provides an all-front access
interface (fibers, power, alarm contact, and management) that complies with international standards.
Table 1-4 explains the front panel features.
Figure 1-2 Cisco ONS 15501 Front Panel
POWER
ALARM OUT
Cisco ONS 15501
FAI L
LOS
-48V
RET
-48V RET
LAN
RS-232
DC connectors shown
with cover removed
53 7 10
1 8 9 11 112 6
68377
4
INVISIBLE LASER RADIATION.
DO NOT VIEW DIRECTLY WITH
OPTICAL INSTRUMENTS.
CLASS 1M LASER PRODUCT.