Measurement of SFP Module Optical Signal Strength<br>

dBm -> mW: mW=10dBm/10 <br>
mW -> dBm: dBm=10 *(Log mW)<br>
Here are some figures recommended by EMC.<br>
<table>
<tr><td>microwatt</td><td> 	milliwatt </td><td>	dBm</td><td> 	Description</td></tr>
<tr><td>1.0</td><td>0.0010</td><td>-30.00</td><td>Loss of Signal</td></tr>
<tr><td>10.0</td><td>0.0100</td><td>-20</td><td></td></tr>
<tr><td>25.1</td><td>0.0251</td><td>-16</td><td>2Gbps minimum accept signal</td></tr>
<tr><td>31.6</td><td>0.0316</td><td>-15</td><td>4Gbps minimum accept signal</td></tr>
<tr><td>50.0</td><td>0.0500</td><td>-13.01</td><td>	 </td></tr>
<tr><td>100.0</td><td>0.1000</td><td>-10.00</td><td>10GB with 5db margin</td></tr>
<tr><td>125.9</td><td>0.1259</td><td>-9.00</td><td></td></tr>
<tr><td>150.0</td><td>0.1500</td><td>-8.24</td><td></td></tr>
<tr><td>200.0</td><td>0.2000</td><td>-6.99</td><td>Normal range of optical signal strength</td></tr>
<tr><td>250.0</td><td>0.2500</td><td>-6.02</td><td></td></tr>
<tr><td>300.0</td><td>0.3000</td><td>-5.23</td><td></td></tr>
<tr><td>350.0</td><td>0.3500</td><td>-4.26</td><td></td></tr>
<tr><td>400.0</td><td>0.4000</td><td>-3.98</td><td></td></tr>
 </table>
Notes: Optical signals get attenuated during transmission.<br>
To ensure the transmission quality, network operators also need to pay attention to the attenuation caused by optical transceivers.<Br>
There is the acceptable light attenuation range of some common modules rate.<br>
10Gbps maximum acceptable signal attenuation: -10dBm<br>
8Gbps maximum acceptable signal attenuation: -13.8dBm<br>
4Gbps maximum acceptable signal attenuation: -15.4dBm<br>
2Gbps maximum acceptable signal attenuation: -18.2dBm<br>
<br><Br>
Some manufactures claim -15dBm min for 10GB, I believe for best practice we should strive for -10dBm if possible.<br>