# Tech Library

We try to collect, documented and share all of our experiences.

## How to calculate optical loss?

Transceiver has a lot of distance variation start from 100 Meters, 10KM, 40KM up to 160KM. This distance variation means each transceiver has ability to handle the optical cable loss. Normally longer optical cable make a higher loss.

In same case 10KM optical cable have the same loss with 40KM optical cable, It's caused quality degradation of the optical cable or low quality of connector and splicing. Below how to calculate optical loss.

1. Optical Power Meter (OPM)

With OPM we will get the real result of optical cable loss. We can see receive power level at one side or both side, so with this technique we must use active equipment such as Router, Switch, Transceiver / SFP and the OPM its self.

Picture 1. Measure optical cable loss with OPM

Picture 2. Measure optical cable loss with receive information (DDM) from router / switch

Loss Formula = Transmit - Receive

Example Transmit A = +1dBm and Receive B = -16dBm, so the loss is

Loss = 1dbm - (-16dBm)

Loss = 17dBm

2. Manual calculation (Prediction Formula)

In some cases we can't use OPM technique, because the equipment or cable or transceiver are still not ready. Don't worry with this way, we can predict how much the optical cable loss.

Optical cable loss coming from the optical cable distance, splicing and connector (OTB or connector). Each components have standard value (see the picture below).

Picture 3. Optical cable loss standard

We provided a simple program to calculate optical cable loss. We can input the wavelength and the cable distance. This simple program can be downloaded from the link below.