Optical Attenuation Reference Guide
"Look Before You Leap"
This guide outlines general best-practice guidelines for optical attenuation. Actual attenuation requirements will vary depending on the specific transmitter output power and receiver sensitivity of the optical modules in use.
Note: The values presented are approximate and provided for reference only. Optical power levels should always be verified—either with an optical power meter or by reviewing transceiver Rx power readings—to ensure they fall within the specified safe operating (dynamic) range of the transceiver prior to final connection.
The "Rule of Thumb" for Loss
Use the following conversion as a baseline for estimating distance loss, but treat it as a starting point only. Because specifications vary, you must always verify these estimates against the actual Rx power readings of your optic in the field.
- 1310 nm Wavelength: 1 dB Attenuator is about 3 km of distance loss
- 1550 nm Wavelength: 1 dB Attenuator is about 5 km of distance loss
Distance (Fiber Span)
40km Optic (1310nm)
40km Optic (1550nm)
80km Optic (1310nm)
80km Optic (1550nm)
≤ 5 km
7 dB
7 dB
Not Recommended
Not Recommended
≤ 10 km
5 dB
5 dB
10 dB
12 dB
≤ 15 km
3 dB
8 dB
10 dB
11 dB
≤ 20 km
2 dB
3 dB
7 dB
10 dB
≤ 30 km
-
-
5 dB
10 dB
≤ 40 km
-
-
2 dB
8 dB
≤ 50 km
-
-
-
5 dB
⚠️ IMPORTANT WARNING FOR LONG-REACH OPTICS
- 40 km transceivers – Do Not Test or Use with ≤ 25 km fiber cables
- 80 km transceivers – Do Not Test or Use with ≤ 60 km fiber cables
Long-reach transceivers have highly sensitive receivers.
Connecting them directly to equipment or using short cables without proper attenuation can:
- Blind the receiver — causing errors and connection issues
- Permanently damage the receiver — this is NOT covered under warranty
How to Protect Your Optic
- Always use the recommended attenuators for short-distance connections
- Follow proper installation guidelines
- If unsure, contact us for recommended attenuation levels