Configuring an Optical Attenuator

This section describes how to configure an optical attenuator.

Calculating the Optical Attenuation

You can calculate the optical attenuation based on the actual optical power.

**Table 1** Description of the Paramater
Name	Description
P(in)min	maximum transmit optical power.
P(out)max	transmission distance.
S	transmission distance.
A	attenuation coefficient. Note that the attenuation coefficient is related to optical fiber types and wavelengths. By default, the attenuation coefficient of a 1310-nm wavelength in a G.652 fiber is 0.45 dBm/km or 0.4 dBm/km; the attenuation coefficient of a 1550-nm wavelength in a G.652 fiber is 0.235 dBm/km or 0.25 dBm/km.
P(in)max	maximum receive optical power, that is, minimum overload point.

The principle for determining whether an attenuator needs to be configured at a transmission point is as follows:

If P(out)max – S x Attenuation coefficient > P(in)max, an attenuator needs to be configured. The optical attenuation is calculated in the following formula: T= P(out)max - S x Attenuation coefficient - P(in)max.

**Table 2** Reference for configuring an attenuator
BOM Number	Description	P(out) max	P(out) min	P(in) min	P(in) max
34060276	eSFP,1310nm,STM1,LC,SM,15km	-8 dBm	-15 dBm	-31 dBm	-8 dBm

If P(in)max of an optical module equals P(out)max, you do not need to configure an attenuator.
You can choose the 5 dBm and 10 dBm attenuators for optical modules on the device.

BOM Number and Description of Attenuators

**Table 3** BOM number and description of attenuators
BOM Number	Description
45030021	Fixed Optical Attenuator,1260nm~1620nm-5dB-LC/PC-45dB
45030022	Fixed Optical Attenuator,1260nm~1620nm-10dB-LC/PC-45dB

This table is for reference only. BOM numbers of attenuators vary with configuration documents.