As promised, here are the results of a small experiment on splicing G.652D and G.657 fibers. Just to recap, this experiment was prompted by the common belief that splicing G.652D to G.657B results in significant loss — reportedly as high as 0.6 dB.
For the experiment, we used: a Fujikura FSM-50S fusion splicer (our daily workhorse), a Fujikura CT-30 cleaver, a Miller FO 103-T-250-J stripper, a Yokogawa AQ7275 optical time-domain reflectometer (which can also generate a stable 0 dBm / 1 mW optical signal), an SNR-PMT-08C optical power meter, two FC/UPC‑to‑SC/APC patch cords for connecting to the OTDR and power meter, two SC‑SC APC adapters, lint‑free Kimwipes wipes, isopropyl alcohol, and an SC/APC‑to‑SC/APC single‑mode patch cord (0.9 mm, G.652D) which we'd be splicing to the other fiber type.
The initial signal level measurements gave us the following readings:
- At 1310 nm: 0.76 mW
- At 1550 nm: 0.81 mW
The photo actually shows 0.80 mW at 1550 nm — the meter was fluctuating between 0.80 and 0.81 mW, but it settled on 0.81 most of the time. Reversing the patch cord gave slightly different results: 0.73 mW at 1310 nm and 0.76 mW at 1550 nm, which I attribute to minor core misalignment in the connectors. When I swapped the connectors back, the readings returned to their original values.
After unpacking the patch cord, we measured it again and got the same numbers — so coiling the fiber with a large radius didn't affect the loss.
Next, as a control test, we cut the patch cord and respliced it — the results stayed the same. We also made another splice with a heat‑shrink protection sleeve — again, no change in optical power levels.
To make sure the results weren't being affected by connector variations, we decided to leave the connectors alone and splice a section of bend‑insensitive fiber directly into the patch cord. Since we'd been splicing this fiber from our splitters into the network, we borrowed a piece from an optical splitter:
This gave us two splices between standard and bend‑insensitive fiber, with the loss split across both joints.
It's worth noting that the splicer might misidentify the fiber type and throw up a loss estimate error. On various forums, professionals recommend forcing the "SM Autocalibrate" mode for this type of splice.
After several splice attempts, we got these power readings:
- At 1310 nm: 0.75 mW
- At 1550 nm: 0.80 mW
Converting these to decibels:
- At 1310 nm: 0.76 mW (−1.19 dBm) → 0.75 mW (−1.25 dBm) = 0.06 dB
- At 1550 nm: 0.81 mW (−0.92 dBm) → 0.80 mW (−0.97 dBm) = 0.05 dB
Keep in mind this is the loss across two splices. So the average loss per splice works out to about 0.03 dB — which is comparable to splicing standard fibers (though admittedly not the best‑quality splices).
Here are a few photos taken during the splicing process:
And finally, a short video: