Cisco ACIP-SM= Installation And Configuration Manual - Page 6

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Cisco ACIP-SM= Installation And Configuration Manual

ACIP Description

Table 2

Limits

Attenuation

Dispersion

1. The product of bandwidth and

distance must be less than 500

MHzkm.

Approximating the ACIP Power Margin

The LED used for a multimode transmission light source creates multiple propagation paths of light,

each with a different path length and time requirement to cross the optical ﬁber, causing signal

dispersion (smear). Higher order mode loss (HOL) results from light from the LED entering the ﬁber

and being radiated into the ﬁber cladding. A worst case estimate of power margin (PM) for

multimode transmissions assumes minimum transmitter power (PT), maximum link loss (LL), and

minimum receiver sensitivity (PR). The worst case analysis provides a margin of error, although not

all of the parts of an actual system will operate at the worst case levels.

The power budget (PB) is the maximum possible amount of power transmitted. The following

equation lists the calculation of the power budget:

The power margin calculation is derived from the power budget minus the link loss, as follows:

If the power margin is positive, as a rule, the link will work.

Table 3 lists the factors that contribute to link loss and the estimate of the link loss value attributable

to those factors.

Table 3

Link Loss Factor

Higher order mode losses

Clock recovery module

Modal and chromatic dispersion Dependent on ﬁber and wavelength used

Connector

Splice

Fiber attenuation

After calculating the power budget minus the data link loss, the result should be greater than zero.

Results less than zero may have insufﬁcient power to operate the receiver.

6 ATM Cable Interface Processor (ACIP) Installation and Conﬁguration

Typical Fiber-Optic Link Attenuation and Dispersion Limits

Multimode

1.0 dB/km

500 MHzkm

PB = PT – PR

PB = –18.5 dBm – (–30 dBm)

PB = 11.5 dB

PM = PB – LL

Estimating Link Loss

Estimate of Link Loss Value

0.5 dB

1 dB

0.5 dB

1 dB/km