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ETA · Last updated November 2026

ETA Fiber Optics Technician, Inside Plant (FOT-ISP): free practice test

FOT-ISP is ETA's technician-level certification for inside plant fiber: multimode and single-mode links in premises, enterprise and data center networks. The 75-question, 2-hour knowledge exam needs 75% and follows ETA's 16-category competency list, from light theory and NEC cable rules to loss budgets, TIA-568 testing and OTDR work. A hands-on course and skills exam at an ETA-approved school are also required; this prep covers only the written exam.

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About the ETA FOT-ISP exam

FOT-ISP is ETA's technician-level certification for inside plant fiber: multimode and single-mode links in premises, enterprise and data center networks. The 75-question, 2-hour knowledge exam needs 75% and follows ETA's 16-category competency list, from light theory and NEC cable rules to loss budgets, TIA-568 testing and OTDR work. A hands-on course and skills exam at an ETA-approved school are also required; this prep covers only the written exam.

What's on the exam

ETA FOT-ISP
Light, Fiber Theory and Fiber Types
7 key facts
Transmitters, Receivers, Passives and PON
7 key facts
Fiber Optic Cables and NEC Requirements
8 key facts
Splicing and Connectors
8 key facts
Installation, Hardware and Safety
8 key facts
Loss Budgets and Data Center Links
7 key facts
Testing, OTDR and Troubleshooting
7 key facts

Each branch is a topic in the official outline. Members see every key fact on the full mind map. Read the free study guide →

How to pass the ETA FOT-ISP exam

  • ETA writes the exam from its FOT-ISP competency list, which cites TIA-568, TIA-526-14, TIA-942, IEEE 802.3 and NEC Article 770 by name. Learn the numbers those documents set: 0.75 dB per mated pair, 0.3 dB per splice, reach per fiber grade.
  • Bring a scientific calculator. dBm conversions, loss budgets, numerical aperture and OTDR distance questions all need log and square root keys.
  • 75% of 75 is a high bar (about 57 correct). Testing and OTDR take up the last two competency categories and appear across others, so practise reading traces and choosing reference methods until they are automatic.
  • Know the data center material: MPO polarity and adapter types, Top of Rack vs End of Row, Uptime Tiers and IEEE multimode reaches for 10, 40 and 100 Gb/s.

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Create a free account after the test: your score by topic, a mistakes bank, the complete study notes for the first topic, flashcards and the RCDD Numbers & Formulas Sheet.

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What's in the premium ETA FOT-ISP prep

Premium ETA FOT-ISP prep is studied one topic at a time. Each step starts with that topic's key notes and flashcard deck, then its own question sets of 25, so you master one topic before you move to the next. When every topic is strong, the 6 full mock exams show you're ready.

3,000practice questions, every answer explained
6full-length mock exams, 75 questions each, timed
800flashcards with spaced repetition, sorted by topic
60comprehensive key notes across 7 topics

Your step-by-step study path

  1. 1
    Light, Fiber Theory and Fiber Types9 key notes, 115 flashcards, then 450 practice questions in 18 sets of 25
    Notes free with an account
  2. 2
    Transmitters, Receivers, Passives and PON9 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25
    Premium
  3. 3
    Fiber Optic Cables and NEC Requirements9 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25
    Premium
  4. 4
    Splicing and Connectors9 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25
    Premium
  5. 5
    Installation, Hardware and Safety8 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25
    Premium
  6. 6
    Loss Budgets and Data Center Links8 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25
    Premium
  7. 7
    Testing, OTDR and Troubleshooting8 key notes, 110 flashcards, then 425 practice questions in 17 sets of 25
    Premium
  8. Final step: 6 full mock exams75 questions each, timed like test day. Pass them, then book your exam.
    Premium
Free with an account

Read the complete ETA FOT-ISP study notes for “Light, Fiber Theory and Fiber Types”

Our first full set of comprehensive notes, about 14 minutes of reading: Refraction and total internal reflection · Fiber construction and grades · Attenuation · Dispersion and bandwidth, a worked exam example, the traps examiners use and a one-minute recap. Create a free account to read it and see how premium notes work before you decide.

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Study tools included

3,000 practice questions

3,000 exam-style questions per exam, organized topic by topic in sets of 25. Every answer explained, with the rule it comes from.

6 full mock exams

6 full-length timed mock exams per exam, with real question counts and time limits, so test day feels like practice day.

Exam Readiness Score

One 0 to 100 number that tells you when you're ready to book. Reach 80 and you're covered by our Pass Guarantee.

800 flashcards + spaced repetition

800 flashcards per exam, in a deck for each topic, that come back right before you'd forget them. Five minutes a day keeps every number fresh.

60 comprehensive key notes

60 key notes per exam, split across its topics and each explained in full: the concepts, worked exam examples, the traps examiners use and a quick recap. Your first set is free with an account.

Mind maps

See the whole exam on one screen: every topic and the facts under it.

Sample questions with answers

These are the questions in the free test above, with answers. Try the test first. You'll learn more by getting some wrong.

1. A multimode fiber data sheet lists a core index of 1.480 and a numerical aperture of 0.200. What is the cladding index?
Answer: 1.467. Rearrange NA = √(n1² − n2²): n2 = √(1.480² − 0.200²) = √(2.1904 − 0.0400) = √2.1504, about 1.467. Subtracting the NA directly from the core index (1.280) or subtracting NA squared from the index itself (1.440) skips the squares. The cladding index is always only slightly below the core index.
2. A data center plans 100 Gb/s links that use shortwave WDM, with four wavelengths between about 850 and 940 nm on one duplex multimode pair. Which fiber grade has its effective modal bandwidth specified across that range?
Answer: OM5. OM5 is wideband multimode fiber: its effective modal bandwidth is specified at 850 nm and at 953 nm, so it supports SWDM over longer reaches. OM4 is laser-optimized only at 850 nm, and OS2 is single-mode fiber that SWDM multimode optics cannot use.
3. A single-mode transmitter launches +2 dBm into a short link with 2.0 dB of loss. The receiver's maximum input (overload) is −3 dBm. What is the minimum attenuation that must be added?
Answer: 3 dB. Received power is +2 − 2.0 = 0 dBm, which is 3 dB above the −3 dBm overload level, so at least a 3 dB attenuator is needed. Subtracting the overload level from the transmit power (5 dB) ignores the loss the link already provides.
4. A passive optical LAN design places an ideal 1:16 splitter between the OLT and the ONTs. What theoretical loss does the splitter add at each output port, before excess loss?
Answer: 12 dB. Splitting loss is 10 × log of the split ratio: 10 log 16 is about 12 dB, because each halving of power costs about 3 dB and 16 is four halvings. Real splitters add excess loss on top, so measured values run higher. 16 dB treats the ratio as decibels.
5. A nonconductive fiber cable will be installed without a raceway in the space above a suspended ceiling that is used for environmental air. Which NEC cable type is required?
Answer: OFNP. A space used for environmental air is a plenum, so NEC Article 770 requires plenum-rated cable, OFNP for nonconductive fiber. Substitution only works downward: plenum cable can replace riser or general-purpose cable, but riser (OFNR) cannot replace plenum.
6. A 48-fiber loose tube cable uses 12 fibers per buffer tube and the TIA-598 color code. Where is fiber 29?
Answer: Green tube, slate fiber. Fiber 29 is 2 × 12 + 5, so it is the fifth fiber in the third tube. The third color is green and the fifth is slate. Counting tubes from zero or swapping tube and fiber colors are the usual slips.
7. In a data center trunk, an adapter mates two MPO connectors with both connector keys facing up. Under TIA-568.3, which array adapter type is this?
Answer: Type B adapter. A Type B array adapter mates the connectors key-up to key-up, which reverses the fiber positions across the mating. A Type A adapter mates key-up to key-down and keeps positions straight through. Type C is a polarity method for trunk cables, not an adapter type.
8. Single-mode fusion splices on a batch of fiber keep showing high estimated loss on a fixed V-groove splicer, even with good cleaves. The fiber's core is slightly off-center in the cladding. What fixes the problem?
Answer: Use a core-alignment (active alignment) splicer. A fixed V-groove aligns the claddings, so any core-to-cladding offset becomes lateral core misalignment and loss. A core-alignment splicer images the cores and moves them into line. More arc power cannot correct offset, and index matching gel is for mechanical splices.
9. A technician must inspect a connector on a patch panel whose far end may be connected to an active laser transmitter. What is the safest way to inspect it?
Answer: Use a video inspection probe and never look at the fiber directly. Infrared communication light is invisible, so you cannot tell by eye whether the fiber is live. A video probe puts the image on a screen, keeping your eye out of the beam; checking with a power meter first is good practice too. Relying on a direct-view scope's filter or on visible glow risks eye injury.
10. A 12 mm diameter inside plant cable with 24 fibers is being pulled through a pathway at its rated tension. Under TIA-568.3, what minimum bend radius applies during the pull?
Answer: 180 mm. Inside plant cables other than 2- and 4-fiber horizontal cables need 15 times the outside diameter under tensile load and 10 times with no load: 15 × 12 mm = 180 mm. 120 mm is the installed (no-load) value, and 20 times is the outside plant rule. The 50 mm figure applies only to small 2- and 4-fiber cables while pulled.
11. A 400 m multimode link at 850 nm has 3 mated connector pairs and 2 splices. Using 3.5 dB/km for the fiber and TIA-568 maximums of 0.75 dB per mated pair and 0.3 dB per splice, what is the maximum allowable link loss?
Answer: 4.25 dB. Fiber: 0.4 km × 3.5 = 1.40 dB. Connectors: 3 × 0.75 = 2.25 dB. Splices: 2 × 0.3 = 0.60 dB. Total 4.25 dB. Counting only 2 mated pairs gives 3.50 dB and leaving out the splices gives 3.65 dB; always count every mated pair, including those at the panels.
12. A designer plans a 120 m 100GBASE-SR4 channel over OM4 between rows. What is the problem?
Answer: It exceeds the 100 m OM4 reach for SR4. IEEE 802.3 limits 100GBASE-SR4 to 100 m on OM4 and 70 m on OM3, so 120 m is out of specification; shorten the route or use single-mode optics. 150 m on OM4 is the 40GBASE-SR4 figure, a common mix-up.
13. An OTDR is set to an index of refraction of 1.4600, but the cable manufacturer specifies 1.4700. The trace shows the far end at 2,000 m. What is the actual fiber length?
Answer: About 1,986 m. OTDR distance is proportional to 1 ÷ IOR. With the index set too low, the OTDR assumes light travels faster and overstates distance: actual length = 2,000 × 1.46 ÷ 1.47, about 1,986 m. Always set the IOR from the cable data sheet before measuring length.
14. An OTDR shows a fusion splice as a 0.08 dB gain when shot from end A and a 0.30 dB loss when shot from end B. What is the splice's actual loss?
Answer: 0.11 dB. A gainer comes from a mode field diameter mismatch, so the true loss is the average of the two directions: (−0.08 + 0.30) ÷ 2 = 0.11 dB, well within the 0.3 dB TIA-568 limit. Adding the two readings as positive values gives 0.19 dB, and forgetting to halve gives 0.22 dB.
15. For a Tier 1 test, a technician set the power meter reference with launch and receive jumpers mated together, then measured the link. TIA-568 calls for the one-jumper method. How does this affect the result?
Answer: It understates loss by about one connection. Referencing with two jumpers (Method A) puts one mated connection into the reference, so it is subtracted from every result and the link reads about one connection low. The one-jumper method (Method B) includes both end connections, which is what TIA-568 limits assume.

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ETA FOT-ISP exam FAQ

How many questions are on the ETA FOT-ISP exam?

75 questions on the knowledge exam, with a time limit of 2 hours. Format: closed book. eta allows scratch paper and a non-programmable scientific calculator. eta publishes only the question count, not the item types; our practice uses 4-option single-best-answer questions. eta requires a hands-on training course and skills exam from an eta-approved school, so this prep covers only the written knowledge exam.

What is the passing score for ETA FOT-ISP?

75% (about 57 of 75 questions).

How much does the ETA FOT-ISP exam cost?

US$155 exam fee (ETA list price); the hands-on course is priced separately by the school. One free retake within one year of the first attempt. Certification term 4 years, with maintenance required. BICSI fees can change without notice, so confirm on bicsi.org before you apply.

Which languages is the ETA FOT-ISP exam offered in?

English. ETA does not list other language versions for this exam; confirm with ETA or your school.

Where do I take the ETA FOT-ISP exam?

An ETA-approved school with an ETA Course Approval, after the required hands-on course; the exam is proctored by an ETA Certification Administrator, online in ETA's Trapeza system or on paper.

Is this ETA FOT-ISP practice test free?

Yes. The 15-question practice test on this page is free, with an explanation for every answer and no signup. A free account also unlocks the complete study notes for the first topic. The full ETA FOT-ISP prep is Premium at $147 a month for this exam.

What's in the premium ETA FOT-ISP prep?

3,000 practice questions organized topic by topic (Light, Fiber Theory and Fiber Types: 450; Transmitters, Receivers, Passives and PON: 425; Fiber Optic Cables and NEC Requirements: 425; Splicing and Connectors: 425; Installation, Hardware and Safety: 425; Loss Budgets and Data Center Links: 425; Testing, OTDR and Troubleshooting: 425), 6 full-length timed mock exams of 75 questions, 800 flashcards and 60 comprehensive key notes split across all 7 topics, plus a mistakes bank and the Readiness Score.

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Exam details are summarized from the official candidate information available in October 2026. BICSI changes formats and fees, so confirm with ETA International (Electronics Technicians Association); certification programs accredited by ICAC to ISO/IEC 17024 before you book. RCDDQuizBank is not affiliated with BICSI or Pearson VUE.

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