ETA OTS Exam Study Guide (2026)
Everything the ETA OTDR Testing Specialist (OTS) tests, topic by topic: what each section covers, the facts that come up most, and how to study it. Pair it with the free 15-question practice test.
The exam at a glance
| Questions | 25 multiple-choice questions |
|---|---|
| Time | 2 hours |
| Passing score | 75% |
| Format | Closed book; scratch paper and a non-programmable calculator are allowed. ETA requires an OTDR testing course and hands-on skills exam at an ETA-approved school, so this prep covers only the written knowledge exam |
| Certifying body | ETA International (Electronics Technicians Association), accredited by ICAC under ISO/IEC 17024 |
| Test provider | ETA-approved fiber training schools with an ETA Course Approval, which run the required OTDR testing course and hands-on skills exam; the written exam is proctored by an ETA Certification Administrator online (Trapeza) or on paper |
Mind map: the whole exam on one screen
Read the complete ETA OTS study notes for “Fiber Optic Safety for OTDR Work”
Our first full set of comprehensive notes, about 12 minutes of reading: Laser classes and the OTDR · Safe inspection · Handling OTDRs and working near live networks · OSHA and electrical hazards, 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.
1. Fiber Optic Safety for OTDR Work
ETA competency area 1.0: CDRH laser classes and hazards, laser safety procedures, basic fiber safety practices, safe handling of OTDRs and test tools, OSHA as the workplace safety agency, and electrical hazards in the fiber work environment. ETA does not publish topic weights.
Key facts
- The FDA's Center for Devices and Radiological Health (CDRH) classifies laser products as Class I, IIa, II, IIIa, IIIb and IV; the higher the class, the greater the hazard.
- OTDRs and loss test sources use infrared lasers, which are invisible and give no blink warning. Never look into a port, connector or fiber end.
- Use a video inspection probe rather than an optical eyepiece microscope, which can focus laser light into the eye.
- Confirm a fiber is dark with a power meter or fiber identifier before inspecting it; a live transmitter at the far end may be on.
- Turn the OTDR laser off or cap the port when not connected, and never connect an OTDR to a fiber with live traffic unless it has a filtered out-of-band test port for that purpose.
- Fiber shards: safety glasses, a dark work mat and a sealed shard container; no eating or drinking at the work area.
- OSHA (Occupational Safety and Health Administration) publishes and enforces US workplace safety regulations.
- Electrical hazards include splicer arcs, charger and AC power at test benches, and nearby energized equipment in telecom rooms and on poles.
Flashcards
Exam tip: Treat every fiber as live until a meter or identifier proves otherwise. Many safety answers follow from that one rule.
2. Transmission, Decibels and Light Principles
ETA competency areas 2.0 and 3.0: parts of a fiber link, transmitters and receivers, gain and loss in dB, power in dBm, light as electromagnetic energy, particles and waves, the spectrum, refraction, index of refraction, reflection angles, total internal reflection and Fresnel reflections.
Key facts
- A fiber link is a transmitter (electrical to optical, LED, VCSEL or laser), the cable plant, and a receiver (photodiode, optical to electrical).
- dB = 10 log (P out / P in). 3 dB loss leaves half, 10 dB one tenth and 20 dB one hundredth of the power.
- dBm is power relative to 1 mW: 0 dBm = 1 mW, -3 dBm = 0.5 mW, -10 dBm = 0.1 mW. Loss in dB = dBm in minus dBm out.
- Light is electromagnetic energy, described both as waves and as particles (photons). Fiber uses near-infrared wavelengths: 850, 1300, 1310, 1490, 1550 and 1625 nm.
- Index of refraction n = speed of light in a vacuum / speed in the material. Fiber is about 1.46 to 1.48, so light travels about 2 × 10^8 m/s.
- Refraction bends light at an index change; angles are measured from the normal. At the critical angle, refracted light runs along the boundary.
- Total internal reflection keeps light in the core when it meets the core-cladding boundary beyond the critical angle.
- Fresnel reflection happens at any index change; a flat glass-to-air end reflects about 4% (about -14 dB). OTDRs see these as spikes.
Flashcards
Exam tip: Memorize three dB anchors (3 dB half, 10 dB tenth, 20 dB hundredth) and you can estimate any power fraction without a log table.
3. Fiber Construction and Characteristics
ETA competency areas 4.0 and 5.0: fiber parts and tensile strength, standards bodies, manufacturing, modes, index profiles and the optical trench, bend-insensitive fiber, dispersion (chromatic and PMD), attenuation and wavelength, micro and macrobends, numerical aperture, and ITU-T G.652.D, G.655 and G.657 fiber.
Key facts
- Telecom fiber: core plus 125 µm cladding, 250 µm or 200 µm coating. Single-mode core about 8 to 10 µm; multimode 50 or 62.5 µm.
- Fiber is made by depositing doped glass in a preform (for example outside vapor deposition or modified chemical vapor deposition) and drawing it into fiber.
- Index profiles: step index (single-mode and some multimode) and graded index (multimode, reducing modal dispersion). Bend-insensitive fibers add a low-index trench in the cladding.
- Attenuation comes from absorption and Rayleigh scattering, which falls as wavelength rises: multimode about 3 dB/km at 850 nm and 1 dB/km at 1300 nm; single-mode about 0.35 at 1310 and 0.2 dB/km at 1550 nm.
- Macrobends are visible bends that leak light, with loss rising strongly at longer wavelengths; microbends are tiny distortions from pressure, crush or cold.
- Chromatic dispersion: wavelengths travel at different speeds. Polarization mode dispersion (PMD): the two polarization states travel at different speeds, important for high bit rates over long links.
- Numerical aperture NA = square root of (n core squared minus n cladding squared); it sets the acceptance cone of light.
- G.652.D standard low water peak single-mode; G.655 non-zero dispersion-shifted for DWDM; G.657 bend insensitive (A compatible with G.652.D, B for tighter bends).
Flashcards
Exam tip: Link fiber facts to the trace: slope is attenuation, a wavelength-dependent step is a bend, and the trench is why modern fiber hides small bends.
Test yourself on these topics
Take the free 15-question ETA OTS test, then save your results to unlock your Readiness Score and the mistakes bank.
4. Connectors, Endfaces and Reflectance
ETA competency area 6.0: connector parts, intrinsic and extrinsic factors, flat, curved (PC/UPC) and angled (APC) endfaces, return loss and reflectance, endface inspection to TIA-455-57 and IEC 61300-3-35, interferometry and Telcordia GR-326 geometry, TIA-568 color code, small form factor connectors, and TIA-568 and ITU-T G.671 loss and reflectance limits.
Key facts
- A connector has a ferrule holding the fiber, a body, a coupling mechanism and a boot; mated pairs meet inside an adapter with an alignment sleeve.
- Intrinsic factors come from the fibers (core size, NA, MFD mismatch); extrinsic factors come from the connector (offset, gap, angle, dirt, endface damage).
Flashcards
Exam tip: With reflectance, more negative is better. Write the limit and the reading on a number line if the signs confuse you.
5. Related Test Equipment and Loss Testing
ETA competency area 7.0: NIST-traceable calibration, continuity testers, non-intrusive live traffic identification, visual fault locators, OLTS operation, patch cords versus measurement quality jumpers, TIA-526-14 one, two and three test jumper references, endface inspection and cleaning, and Tier 1 and Tier 2 testing.
Key facts
- Test equipment calibration should be traceable to NIST so that power readings are comparable and defensible.
- Continuity can be checked with a fiber tracer, a VFL or an OLTS. A clip-on fiber identifier detects live traffic and direction through a small bend without disconnecting.
Flashcards
Exam tip: Match each tool to its question: is there light (identifier), where is the break up close (VFL), how much loss (OLTS), where is every event (OTDR).
6. OTDR Operation and Settings
ETA competency areas 8.1, 8.2, 8.6, 8.7 and 8.8: how an OTDR works, trace versus schematic or icon displays, wavelength, pulse width and index of refraction settings, automatic versus manual mode, and real-time versus averaging.
Key facts
- An OTDR sends light pulses and measures returning Rayleigh backscatter and Fresnel reflections against time, converting time to distance with the index of refraction.
- Distance = (speed of light in a vacuum × time) / (2 × index of refraction); the 2 accounts for the round trip.
Flashcards
Exam tip: For each setting ask what it trades: pulse width trades resolution for range, averaging trades time for noise.
7. OTDR Trace Analysis and Dead Zones
ETA competency areas 8.3, 8.4 and 8.5: the primary trace signature, reflective and non-reflective events, dead zones and the settings that affect them, and evaluating event loss and gain with bidirectional testing.
Key facts
- Trace signature: initial reflection at the OTDR port, sloping backscatter (fiber attenuation), events, then the end reflection and noise floor.
- Reflective events (spikes) are connectors, mechanical splices, cracks and open ends; non-reflective steps are fusion splices and bends.
Flashcards
Exam tip: Read every trace left to right: port, launch cable, link events, receive cable, end. Name each event's type before measuring it.
8. Launch and Receive Cables and Link Measurement
ETA competency area 8.9 with related reporting: why launch and receive cables are needed to measure connector Fresnel reflectance and loss, cable length selection, marker placement for end-to-end loss, and documenting results.
Key facts
- A launch cable lets the trace recover from the OTDR port reflection so the first link connector's loss and reflectance can be measured.
- A receive cable at the far end gives backscatter after the last connector, so its loss can be measured.
Flashcards
Exam tip: If a question says a connector couldn't be measured, ask first whether a launch or receive cable was missing or too short.
How to pass
- Each of the 25 questions is worth 4%, so 7 wrong answers means a fail. With almost 5 minutes per question, sketch the trace for any OTDR scenario before choosing.
- Over half of the competency list is background: safety, light, fiber, connectors and loss test sets. Don't study only OTDR traces.
- Know the named standards: TIA-526-14 one, two and three test jumper references (Annexes A, C and B), Telcordia GR-326 endface geometry, IEC 61300-3-35 inspection and TIA-568 loss and reflectance limits.
- For every OTDR setting (wavelength, pulse width, index of refraction, averaging, auto versus manual), learn what it changes on the trace and the trade-off it brings.
Frequently asked questions
How long should I study for the ETA OTS exam?
Most working candidates need 4 to 8 weeks at 45 to 60 minutes a day. Book your exam once your Readiness Score has stayed at 80 or higher for about a week.
Can I take the ETA OTS exam online?
BICSI's v15 handbook describes the RCDD exam at Pearson VUE test centers, not remote proctoring. Format: closed book; scratch paper and a non-programmable calculator are allowed. eta requires an otdr testing course and hands-on skills exam at an eta-approved school, so this prep covers only the written knowledge exam. Check pearsonvue.com/bicsi for the options in your country.
What score do I need to pass the ETA OTS exam?
75%. The exam has 25 multiple-choice questions and a time limit of 2 hours.
What are the most tested topics?
The outline covers fiber optic safety for otdr work, transmission, decibels and light principles, fiber construction and characteristics, connectors, endfaces and reflectance, related test equipment and loss testing, otdr operation and settings, otdr trace analysis and dead zones, launch and receive cables and link measurement. Use the free practice test to see which ones you need most.
The premium ETA OTS study path
Premium ETA OTS 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.
Your step-by-step study path
- 1Fiber Optic Safety for OTDR Work8 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Notes free with an account
- 2Transmission, Decibels and Light Principles8 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 3Fiber Construction and Characteristics8 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 4Connectors, Endfaces and Reflectance8 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 5Related Test Equipment and Loss Testing7 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 6OTDR Operation and Settings7 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 7OTDR Trace Analysis and Dead Zones7 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 8Launch and Receive Cables and Link Measurement7 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- Final step: 6 full mock exams50 questions each, timed like test day. Pass them, then book your exam.Premium
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- The RCDD exam: full prep for the v15 blueprint
- 3,000 practice questions + 6 full mock exams per exam
- 800 flashcards + 60 key notes per exam, by topic, plus mind maps
- Spaced repetition + mistakes bank
- Readiness Score & detailed reports
- Video lessons as they release
- Content updates during your access
- 5 bonuses: numbers and formulas sheet, standards atlas, study planner and more
- Pass Guarantee: complete the prep, pass or 100% back
Renews once a year until you cancel. We email you before each renewal. Cancel any time from your account; you keep access until the end of the year you've paid for.
Summarized from BICSI's official candidate information and the rules cited, checked October 2026. Confirm current requirements with ETA International (Electronics Technicians Association), accredited by ICAC under ISO/IEC 17024.