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The FOD exam has 80 questions and runs 2 hours.
These 10 free FOD questions are organized by exam domain, so you can see how each part of the Fiber Optics Designer (FOD) blueprint is tested. Reveal the answer and explanation under each question.
To limit source-current-induced chirp, a transmitter specification requires separate optical-generation and data-modulation functions. A proposed electroabsorption-modulated laser (EML) has a steadily biased DFB laser and a separately driven absorber on the same chip. How should the reviewer assess this source?
Correct answer: D - Accept the architecture, but verify its chirp and link performance.
A material schedule for a legacy OM2 backbone with Cisco 1000BASE-LX/LH optics lists ordinary 50-µm duplex patch cords. The backbone is within the supported reach, and its connector condition, insertion loss, and received power meet the application limits. Which proposal supplies the required launch with the least disruption?
Correct answer: D - Install manufacturer-specified 50-µm mode-conditioning cords at both ends.
Under the 2023 NEC, a design routes unlisted, all-dielectric outside-plant optical cable to an indoor enclosure 40 ft from the point of entrance. An interior segment runs exposed in the return-air space above a suspended ceiling. The design relies on 770.48(A), and no raceway exception applies. Which review conclusion is correct?
Correct answer: B - Require a transition to OFNP cable before the cable enters the plenum.
While investigating intermittent loss, a technician disconnects a fiber and reaches for a direct-view inspection microscope. The local port shows link down, but the remote transmitter remains enabled. What must happen before the technician looks through the microscope?
Correct answer: C - Isolate the optical sources and verify that the fiber is dark.
A sliding fiber tray passes its closed-position loss test. During the required full-extension access check, however, its pigtails become taut and one bend tightens to 22 mm. The assembly specification requires a 30-mm minimum radius and an anchored incoming cable. Which redesign addresses the acceptance failure?
Correct answer: D - Add managed service slack and guides that preserve cable anchoring and the specified radius.
Two departments have separate duplex-fiber connections to different ports of a Layer-2 switch. The links pass optical testing, but both departments still share one Layer-2 broadcast domain. They need separate broadcast domains and IP communication between their two subnets. Which arrangement provides both functions?
Correct answer: A - Assign separate VLANs; route between their subnets with a Layer-3 device.
Commissioning finds two Cisco BX10-U modules on a 6.4-km, single-fiber G.652 link. Passive tests confirm acceptable attenuation at the BX10 operating wavelengths. The host ports support all the listed module families, and one installed BX10-U will remain. Which replacement should be ordered for the other end to correct the wavelength pairing?
Correct answer: D - One Cisco BX10-D: 1490-nm transmit and 1310-nm receive.
A storage refresh adds NVMe over Fibre Channel to a 32GFC SAN that already carries FCP/SCSI. The HBAs, arrays, switches, and firmware support concurrent operation. Port speed and optical modules are unchanged, and the existing duplex OM4 channels meet all applicable reach and optical limits. What does adding NVMe/FC require of the cabling?
Correct answer: A - Keep the qualified duplex OM4 channels for both storage protocols.
A campus must keep 24 duplex optical circuits available after either of two physically independent cable routes is cut. Each surviving route must carry all 24 circuits, using two fibers per circuit without wavelength sharing. At least 25% of each route's installed fibers must remain unassigned. Which is the smallest offered cable count for each route?
Correct answer: C - 72 fibers
An optical design at 1550 nm has transmitter output from −5 to +1 dBm and path loss from 1 to 4 dB before any added attenuator. Receiver sensitivity is −15 dBm; maximum permitted input is −3 dBm. The design requires at least 2 dB above sensitivity in the weakest-signal condition. Treat the offered attenuator losses as exact and assume the other application limits are met. Which fixed attenuator satisfies both the weak-signal margin and the overload limit?
Correct answer: B - 3.5 dB
The FOD exam also covers these domains. Drill them in the full free practice test:
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