Optical Return Loss and Connector Reflectance
Combines connector reflectances in linear power and converts the result to positive link ORL.
Example
You enter
- Mated connector pairs 4
- Reflectance per connector (negative dB) -50
- Unmated flat ends 1
- Fiber index of refraction 1.468
- Required link ORL (dB) 32
- APC reflectance per connector (negative dB) -60
You get
- Bare-end Fresnel reflection 3.60 % (-14.4 dB reflectance)
- Connector-only link ORL 44.0 dB -- PASS
- ORL with unmated end(s) 14.4 dB -- FAIL
- All-APC link ORL 54.0 dB
Checked against published worked examples from: Experior Photonics, Inc. (L. Cartellieri).
Details, formula, and sources
ScopeIncluding the Fresnel reflection from an unmated glass end. Four -50 dB connectors give about 44 dB ORL; one open end dominates them and drops the link to about 14.4 dB. Transceiver requirements, measured reflectance, and test standards govern.
Formula or tablebare-end Fresnel R = ((n - 1)/(n + 1))^2; event reflectances convert by 10^(dB/10), add in linear power, and link ORL = -10 log10(sum R).
Source and editionFresnel reflection and linear addition of reflected optical powers.
Free accessA Fresnel ratio and power/dB conversions.
What governsEstimate. AHJ and licensed professional govern.
API field namesconnector_count, connector_reflectance_db, unmated_end_count, fiber_index, required_orl_db, apc_reflectance_db, fresnel_reflectance_pct, connector_only_orl_db, with_unmated_orl_db, apc_orl_db
- Nominal event reflectance cleanliness, endface geometry and mating condition alter itmeasurement and connector data
- No round-trip attenuation distant reflections are conservatively not reducedthe simplified link model
- Equipment response excluded laser sensitivity to reflection is product-specificthe transceiver requirement