Optical Communication Products · Shenzhen, China
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Measured fibre by fibreMPO/MTP Loopback Module — FOT Fiber Optic
Configure the assembly below — fibre count, type, polish, polarity, gender, jacket and length all update the specification table live.

MPO/MTP Loopback Module

SKU: FOT-MPO-LPB · Test & Maintenance

Loop an MPO port back on itself for BER and port testing.

12FFibre count
≤ 0.5 dBLoop insertion loss
PassiveNo power needed
Type A/BLoop mapping
Fibre count
12F8F16F24F
Fibre type
OM4 multimodeOM3 multimodeOM5 widebandOS2 single-mode (G.652.D)G.657.A1 bend-insensitive
Polish
UPC / PC (flat)APC (angled, 8°)
Gender
Female (unpinned)Male (pinned)
Attenuation
0 dB (through loop)with 5 dB attenuationwith 10 dB attenuationwith 15 dB attenuation
Configured part numberFOT-MPO-LPB
Request a Quote Request Datasheet
Ships worldwide
Built to your configuration
3-year warranty

Product Overview

A loopback returns each transmit fibre to its paired receive fibre inside a single MPO plug, so a port can be tested end-to-end without a link partner. It is the standard tool for board-level test, for proving a transceiver before you blame the fibre, and for burning in a new switch before it goes live.

Assemblies are built on US Conec MTP® ferrules and terminated in a controlled environment, then measured fibre by fibre. Interferometry checks the three geometry parameters that decide whether a multi-fibre ferrule mates properly — radius of curvature, apex offset and fibre height — and every end face is inspected and graded to IEC 61300-3-35 before the dust cap goes on.

Fibre count, fibre type, polish, polarity, gender, jacket rating, leg length and overall length are all build options rather than catalogue limits. Use the selector above to configure the exact assembly and the specification table will follow your choices; the measured test report ships with the cable.

Technical SpecificationsUpdates with your selection

Optical
Fiber Count12F
Fiber TypeOM4 50/125 µm laser-optimised multimode
Wavelength850 / 1300 nm
Insertion Loss≤ 0.5 dB per loop
Return Loss≥ 30 dB multimode / ≥ 50 dB single-mode
Connector PolishUPC / PC — flat polish
PolarityPosition 1↔12, 2↔11, 3↔10, 4↔9 — reversed, so TX 1–4 returns to RX 9–12
Mechanical & Environment
ConnectorUS Conec MTP® / MPO, female (unpinned)
HousingMoulded shell with integral dust cap and lanyard
Loop FibreInternal, potted — nothing to snag or coil
Operating Temp-10 °C to +60 °C
ComplianceIEC 61754-7, TIA-604-5, RoHS
Jacket ColourAqua / Violet
Testing, Quality & Supply
Optical Test100% — every fibre measured for insertion loss and return loss before shipment
Ferrule GeometryInterferometer-verified: radius of curvature, apex offset and fibre height to IEC 61755-3
End-Face InspectionEvery ferrule inspected and graded to IEC 61300-3-35
Test ReportPer-fibre measured data supplied with the assembly, traceable to the serial number
Connector SourceUS Conec MTP® ferrules; genuine-brand or FOT MPO to your preference
CustomisationFibre count, type, polish, polarity, gender, jacket, leg length and overall length built to order
Lead TimeStock configurations 3–5 days; custom builds 7–10 days
Warranty3 years

Ordering Information

Part NumberConfigurationFibre countAvailability
FOT-MPO-LPBStandard configuration12FBuild to order
FOT-MPO-LPB-8FFibre count: 8F8FBuild to order
FOT-MPO-LPB-16FFibre count: 16F16FBuild to order
FOT-MPO-LPB-24FFibre count: 24F24FBuild to order
FOT-MPO-LPB-OM3Fibre type: OM3 multimode12FBuild to order
FOT-MPO-LPB-OM5Fibre type: OM5 wideband12FBuild to order
FOT-MPO-LPB-OS2Fibre type: OS2 single-mode (G.652.D)12FBuild to order
FOT-MPO-LPB-657A1Fibre type: G.657.A1 bend-insensitive12FBuild to order

Part numbers are indicative. Send us the fibre count, type, polish, polarity, gender, jacket and length and we confirm the exact build code on the quotation.

Quality & What's in the Box

Measured Fibre by Fibre

Insertion loss and return loss recorded for every fibre, not sampled.

Geometry Verified

Interferometer data on ferrule radius, apex offset and fibre height.

Inspected & Graded

Every end face checked against IEC 61300-3-35 before packing.

Packaging

Dust-capped, coiled on a reel or in a bag with the test report and pulling sock.

Typical Applications

Data Centre Spine & Leaf

Parallel 40G/100G/400G/800G backbone between spine, leaf and top-of-rack panels.

AI / GPU Clusters

Rail-optimised accelerator fabrics where one switch port breaks out to several GPUs.

Structured Cabling

Pre-terminated backbone that installs in hours instead of days, with the loss budget known up front.

Test & Commissioning

Loopbacks, attenuators and inspection for proving ports before the link goes live.

Frequently Asked Questions

Why would I want an attenuated loopback?

Because a zero-loss loop can overload the receiver. Short-reach single-mode optics in particular are specified for a link that has some loss in it; loop them straight back and the receive power can sit above the overload point, which produces errors that look like a fault but are not. Add 5–10 dB and test in the range the optic is actually designed for.

Does the loop mapping matter?

Yes. The loop has to return each transmit lane to the correct receive lane for the module's lane assignment. Tell us the transceiver type on the RFQ — a 12F loop wired for a 100G-SR4 is not the same as one wired for a 400G-SR8.

How is the assembly labelled?

Both ends carry a printed label with the part number, fibre count, fibre type, polarity type and the serial number, and breakout legs are individually numbered. Tell us your own labelling convention on the RFQ and we print to it — it costs nothing and it saves an afternoon at installation.

Can I get free samples before ordering volume?

Yes. We supply qualification samples so you can measure the loss and check the fit in your own panels before committing. Per-order test reports are standard, and sample reports can be provided in advance for tender documentation.

Related MPO / MTP Products

MPO/MTP Fixed Attenuator
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MPO/MTP Fixed Attenuator

MPO/MTP Cleaner & Inspection Kit
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MPO/MTP Cleaner & Inspection Kit

MPO/MTP Trunk Cable
Trunk & Jumper Cables

MPO/MTP Trunk Cable

MPO/MTP Bundle / Multi-Leg Trunk Cable
Trunk & Jumper Cables

MPO/MTP Bundle / Multi-Leg Trunk Cable

Request a quote for this part

Tell us the platform and the quantity. An engineer checks the part against your switch and software version before quoting — if it will not work, we say so.

Goes to our engineers and the quotation desk together. Replies come from sales@topnetsystem.com, usually within one working day.