Field Notes
Learning fiber inside out, and teaching it forward.
WHY THIS PAGE
I'm a working Field Service Technician and a Washington State Electrical Administrator, Telecommunications (09) specialty — L&I license PORTEM*744M3. Most of what I know about fiber I learned the hard way: on a ladder, at a splice tray, or staring at an OTDR trace that made no sense yet.
These notes are the explanations I wish someone had handed me on day one, written for the people doing the same work — Field Service Network Specialists, Field Service Network Technicians, and Field Service Technicians. Plain language first, then the mechanism underneath, then one worked example. Everything comes from public standards and general trade practice; every number is labeled for what it is.
TWO WORKING LIVES
Part of my working life happens at a desk. Quantum physics, AI, programming — I value that work, and I think it matters. But it lives in the abstract and in software. You can do it for a long time without touching anything you could hold in your hand.
The other part happens in the field, and fiber is the opposite. A fiber-optic network is tangible: glass in a buffer tube, a drop on a pole, a splice in a closure, light at an ONT. It is practical, and it actually connects people.
Neither half is the point on its own. The point is the combination: the big ideation that comes from inside work — from being an indoor cat — joined with the practical, hands-on knowledge that comes from every aspect of even the most basic residential install: the route the drop takes, the light that reaches the ONT, the wall it goes through, the person waiting on it.
FIELD NOTES
TIA-598 TRAINER
The fiber color code is the alphabet of the splice tray, and like any alphabet it only gets fast with reps. The trainer drills it three ways — color to position, position to color, and the full sequence in order — with instant feedback and a score per round. Big buttons, built for a phone in a truck cab.
LIGHT SHOW
Light Show is a training artifact built by an FST: a puzzle game where you route light from the OLT to the customer's ONT and every splice, connector, and splitter costs real dB. If the light-loss budget note is the theory, Light Show is the practice round.
FIBER IN THE UNITED STATES — A TIMELINE
Fifty-odd years from a strand of Corning glass to a federal buildout: sixteen milestones in five eras. Every date was checked against the sources each entry links.
Era 1 of 5: Glass that carries light, 1970–1980
Glass that carries light 1970–1980
Fiber starts as a materials problem: glass pure enough that light survives a kilometer of it. Once that is solved, the phone companies put real calls on it within seven years.
Corning makes glass clear enough to signal through
A Corning Glass Works team — Robert Maurer, Donald Keck, and Peter Schultz among them — drew a titanium-doped silica fiber that lost about 17 dB per kilometer, under the roughly 20 dB/km threshold that made fiber practical for communication.
Sources: Wikipedia — Optical fiber · IEEE ETHW — Fiber Optics
First live telephone traffic over fiber
GTE carried live telephone calls over fiber in Long Beach, California, at 6 Mb/s. AT&T followed quickly with a fiber system in Chicago.
Sources: Wikipedia — Fiber-optic communication · IEEE ETHW — Fiber Optics
Fiber carries the Lake Placid Olympics
AT&T installed a public demonstration system in Lake Placid, New York, in 1979, and it carried multiple television signals during the 1980 Winter Olympics.
Sources: IEEE ETHW — Fiber Optics
The long haul 1983–1988
Fiber leaves the demonstration city and starts tying cities, then continents, together. The links still turn light back into electricity every few dozen kilometers — and the device that ends that habit is invented in the same years.
MCI lights New York to Washington
MCI, working with Corning, opened a commercial fiber-optic system between New York and Washington at a wavelength of 1.3 micrometers. AT&T soon answered with a competing line.
Sources: IEEE ETHW — Fiber Optics
The erbium-doped fiber amplifier
Groups at the University of Southampton and AT&T Bell Laboratories demonstrated gain in erbium-doped fiber. An amplifier made of fiber boosts the light as light, so a long link no longer has to convert to electricity and back at every repeater.
Sources: Wikipedia — Optical amplifier · Wikipedia — Optical fiber
TAT-8 crosses the Atlantic in glass
The first transatlantic fiber-optic cable, built by a consortium led by AT&T, France Télécom, and British Telecom, linked the United States, the United Kingdom, and France. Each fiber carried 280 Mb/s of traffic — about 40,000 telephone circuits for the system — through regenerators spaced roughly 40 km apart.
Sources: Wikipedia — TAT-8 · IEEE ETHW — Fiber Optics
Many colors on one strand 1996
Amplifiers and wavelength-division multiplexing arrive together: one fiber carries many colors of light, each its own channel, and the amplifiers boost them without unpacking them. Capacity stops growing by the decade and starts growing by the year.
Amplifiers go under the Atlantic
TAT-12/13 entered operation carrying 2 × 5 Gb/s, the first cables on the transatlantic route to use erbium-doped fiber amplifiers.
Sources: Wikipedia — TAT-12/13
Dense WDM goes commercial
Ciena delivered the first commercial dense wavelength-division multiplexing (DWDM) system on Sprint's network: many wavelengths, each an independent channel, sharing a single fiber.
Sources: Wikipedia — Wavelength-division multiplexing · Wikipedia — Ciena
Fiber to the home 1998–2016
The standards bodies work out how to share one fiber among many homes without any powered equipment in the field — the passive optical network — and carriers start running glass all the way to the house.
BPON: a passive optical network standard
ITU-T approved G.983.1, broadband PON, building on fiber-to-the-home work the Full Service Access Network (FSAN) group began in 1995: one fiber from the office, split passively among many homes.
Sources: ITU-T — G.983.1 · Wikipedia — Passive optical network
GPON and EPON
ITU-T G.984.1 defined gigabit-capable PON in March 2003, and the IEEE ratified Ethernet PON (802.3ah) in 2004 — two standards families built on the same passive split.
Sources: ITU-T — G.984.1 · Wikipedia — Passive optical network
FiOS lights Keller, Texas
Verizon launched FiOS fiber internet service in Keller, Texas, in 2004, and added FiOS TV there in September 2005.
Sources: Wikipedia — Verizon Fios
Google Fiber comes to Kansas City
Google Fiber introduced service in the Kansas City metropolitan area in 2012 and grew to twenty area suburbs within three years.
Sources: Wikipedia — Google Fiber
XGS-PON: ten gigabits both ways
ITU-T approved G.9807.1, XGS-PON: a passive optical network at up to 10 Gb/s, symmetric — the same rate upstream and downstream.
Sources: ITU-T — G.9807.1 · Wikipedia — Passive optical network
Capacity, and public money 2018–2023
At the top of the network a single cable now carries terabits per fiber pair. At the edge, the open question is who still has no line at all — and federal programs put billions behind reaching them.
MAREA: 160 Tb/s from Virginia Beach
MAREA, finished in September 2017 between Virginia Beach and Sopelana, Spain, began operating in February 2018. Its eight fiber pairs were designed for 160 Tb/s in total — 20 Tb/s per pair.
Sources: Wikipedia — MAREA
RDOF Phase I awards $9.2 billion
The FCC's Rural Digital Opportunity Fund Phase I auction (Auction 904) ended, awarding $9.2 billion in support, paid out over ten years, to 180 winning bidders. More than 85 percent of the locations are in areas where the winner committed to gigabit service.
BEAD: $42.45 billion for broadband
The Infrastructure Investment and Jobs Act, signed November 15, 2021, funded NTIA's Broadband Equity, Access, and Deployment program at $42.45 billion. In June 2023, NTIA announced allocations for all 56 states and territories.
Sources: Wikipedia — Infrastructure Investment and Jobs Act · NTIA — BEAD Program
GLOSSARY
66 terms and 39 equations from my own study notes — fiber and PON, electrical theory for the telecom administrator exam, the NEC articles that govern communications wiring, and the quantum physics I keep next to them. Every equation has a legend: each symbol, and its unit where it has one.
Showing 66 of 66 terms
- Ampere-turns (magnetomotive force)
Magnetomotive force: the number of turns in a coil times the current in amperes. Rearrange to solve for current or turns.
Magnetomotive force is turns times current.
- ℱ
- magnetomotive force (ampere-turns)
- N
- number of turns
- I
- current (amperes, A)
- Antenna systems (NEC 810)
The NEC article for radio and television receiving equipment, antenna masts, lead-in conductors, grounding, bonding, and satellite receiving systems.
- Attenuation (optical)
The loss of optical signal power along a fiber span, written as an attenuation coefficient in dB/km — about 0.35 dB/km at 1310 nm and 0.20 dB/km at 1550 nm. A 20 km run at 1310 nm loses 7 dB in the fiber alone, before any connector or splice losses.
Power falls off exponentially with distance: every kilometer multiplies it by the same fraction, set by α.
- P(L)
- optical power at distance L from the source (linear units, e.g. mW)
- P0
- launch power at the source (linear units, e.g. mW)
- α
- attenuation coefficient (dB/km)
- L
- fiber span length (km)
- Bell states
The four maximally entangled two-qubit states, which form an orthonormal basis for two-qubit systems. Applying H then CNOT to |00⟩ produces the first of them.
All four Bell states: equal blends of matching (Φ) or opposite (Ψ) qubit values, with a plus or minus sign.
- |Φ±⟩
- the two Bell states built from |00⟩ and |11⟩
- |Ψ±⟩
- the two Bell states built from |01⟩ and |10⟩
- |00⟩, |11⟩
- two-qubit basis states: both qubits 0; both qubits 1
- |01⟩, |10⟩
- two-qubit basis states with the qubits different
- ±
- plus or minus: one sign gives each state of the pair
- Bit-flip code (3-qubit)
Protects one logical qubit against a single bit-flip error by encoding it across three physical qubits. Measuring the stabilizers Z₁Z₂ and Z₂Z₃ (parity checks) detects and corrects an error on any one of the three without collapsing the logical state.
Logical 0 is stored as three physical zeros, logical 1 as three ones.
- |0⟩L, |1⟩L
- the logical 0 and logical 1 states
- |000⟩, |111⟩
- three physical qubits, all 0; all 1
- Bloch sphere
Any pure qubit state written in spherical coordinates: the polar angle sets the mix of |0⟩ and |1⟩, the azimuthal angle the relative phase. The north pole is |0⟩, the south pole is |1⟩, and the equator is maximum superposition.
Any pure qubit state is a point on a sphere, fixed by two angles.
- |ψ⟩
- the qubit's state (a ket)
- |0⟩
- the basis state 0 (a ket: a state vector)
- |1⟩
- the basis state 1
- θ
- polar angle, from 0 to π: the mix of |0⟩ and |1⟩
- φ
- azimuthal angle, from 0 to 2π: the relative phase
- cos, sin
- cosine and sine
- e
- Euler's number, the base of the natural logarithm (≈ 2.718)
- i
- the imaginary unit, √−1
- Capacitive reactance
A capacitor's opposition to AC current flow, in ohms. It decreases as frequency increases; with a capacitive load, current leads voltage.
Reactance is one over 2π times frequency times capacitance — so it falls as frequency rises.
- XC
- capacitive reactance (ohms, Ω)
- f
- frequency of the AC signal (hertz, Hz)
- C
- capacitance (farads, F)
- π
- pi, the circle constant (≈ 3.14159)
- Cascaded splitters
Splitters in series — for example a 1:4 feeding four 1:8s, which gives an effective 1:32 split. Their losses add cumulatively.
Two splitters in a row lose the sum of their losses, each set by its own split ratio.
- ILcascade
- total insertion loss of the cascade (dB)
- IL1, IL2
- insertion loss of the first and second splitter stage (dB)
- N1, N2
- split ratio of the first and second stage
- log10
- base-10 logarithm
- CATV and radio distribution (NEC 820)
The NEC article for community antenna television and radio distribution systems — coaxial CATV or radio distribution.
- Class 1 power-limited circuits (NEC 724)
The NEC article for Class 1 power-limited, remote-control, and signaling circuits.
- Class 2 and Class 3 power-limited circuits (NEC 725)
The NEC article for Class 2 and Class 3 power-limited circuits — control, signaling, and low-voltage control wiring.
- Class 4 fault-managed power (NEC 726)
The NEC article for Class 4 fault-managed power systems.
- CNOT (controlled-NOT) gate
The fundamental two-qubit entangling gate: it flips the target qubit when the control qubit is 1. Applying H then CNOT to |00⟩ produces a Bell state.
CNOT leaves |00⟩ and |01⟩ alone and swaps |10⟩ with |11⟩.
- CNOT
- the controlled-NOT gate, a 4×4 matrix acting on two qubits
- Coaxial cable
Cable with a copper core and shielding, carrying electrical signals.
- Communications circuits (NEC 805)
The NEC article for communications wiring from the service point to terminal equipment: cable types, building pathways, listing, separation, and installation methods for voice and data circuits.
- Communications systems, general requirements (NEC 800)
The NEC article for scope and definitions shared across communications systems; grounding and bonding; equipment and cable listing; protection at the building entrance; cable installation and separation; and references that apply across the later Chapter 8 articles. When a rule is common to several communications technologies, start here.
- Copper cable attenuation
Signal loss per unit length in copper cable, which generally increases with frequency. In the simplified model, the √f term models conductor (skin-effect) loss and the f term models dielectric loss; the constants depend on the cable's construction and materials.
Copper loss climbs with frequency: a square-root part from the skin effect plus a straight-line part from the dielectric.
- α
- attenuation: signal loss per unit length (dB/m or dB/ft)
- f
- frequency of the transmitted signal (hertz, Hz)
- k1, k2
- constants set by the cable's construction and materials
- Critical angle (θc)
The angle at the core–cladding boundary beyond which light is totally internally reflected back into the core. It is set by the refractive indices of the core and the cladding.
The critical angle is the angle whose sine is the cladding's index divided by the core's index.
- θc
- critical angle at the core–cladding boundary (degrees)
- n1
- refractive index of the core (dimensionless)
- n2
- refractive index of the cladding (dimensionless)
- arcsin
- inverse sine: the angle whose sine is the value given
- Decibel (dB)
A power ratio on a logarithmic scale. Doubling power is approximately +3 dB, halving it approximately −3 dB, and multiplying it by ten is +10 dB.
A change in dB is ten times the base-10 log of the power ratio.
- ΔPdB
- change in power, in decibels (dB)
- P1
- initial power level (watts, W)
- P2
- final power level (watts, W)
- log10
- base-10 logarithm
- Decoherence
The loss of a qubit's quantum state through interaction with its environment.
- Dense wavelength-division multiplexing (DWDM)
Carrying many wavelengths of light on one fiber at once. A single single-mode strand with DWDM can carry more than 100 Tbps in laboratory conditions.
- Deutsch algorithm
Determines in a single query whether a function f:{0,1}→{0,1} is constant or balanced — something that requires two queries classically. The function is encoded as an oracle gate.
The oracle leaves the input alone and XORs f of the input into the output qubit.
- Uf
- the oracle: a gate that encodes f
- f
- a function from {0, 1} to {0, 1}
- |x⟩, |y⟩
- the input qubit and the output qubit
- ⊕
- XOR: addition modulo 2
- Electrical power
The rate at which a circuit delivers energy, in watts. With any two of voltage, current, and resistance known, the identities give the power.
Power is voltage times current — or current squared times resistance, or voltage squared over resistance.
- P
- power (watts, W)
- V
- voltage (volts, V)
- I
- current (amperes, A)
- R
- resistance (ohms, Ω)
- Entanglement
Once two qubits are entangled, measuring one instantly determines the state of the other, regardless of physical separation. This is not faster-than-light signalling: no classical information is transmitted.
- Fiber-optic cable
Cable that transmits data as pulses of light through ultra-pure glass or plastic strands — light through glass, where copper carries electricity through metal.
- Fidelity (quantum)
How close an actual, possibly mixed, state is to the ideal state. F = 1 is a perfect qubit; F = 0.5 is completely mixed (classical). Error correction requires fidelity above the fault-tolerance threshold (~99.0–99.9% depending on the code).
Fidelity measures how much of the ideal state survives in the actual one.
- F
- fidelity, from 0 to 1
- |ψ⟩
- the ideal state (a ket)
- ⟨ψ|
- the bra: the conjugate transpose of |ψ⟩
- ρ
- the actual, possibly mixed, state (a density matrix)
- Fire-resistive cable systems (NEC 728)
The NEC article for circuit-integrity, fire-resistive cable — cable that must survive fire exposure.
- GPON
A gigabit passive optical network. Upstream and downstream travel on separate wavelengths — 1310 nm upstream, 1490 nm downstream.
- Grover's algorithm
Searches an unsorted database of N items in O(√N) queries where classical search needs O(N) — a quadratic speedup: about 2³² steps instead of 2⁶⁴ for 2⁶⁴ entries.
Run about π/4 times the square root of N iterations, rounded down, then measure.
- k
- the optimal number of Grover iterations before measuring
- N
- the number of items searched
- ⌊ ⌋
- floor: round down to a whole number
- π
- pi, the circle constant (≈ 3.14159)
- Hadamard gate
A single-qubit gate that creates an equal superposition from a basis state.
The Hadamard matrix: all entries ±1, scaled by one over root two.
- H
- the Hadamard gate matrix
Hadamard turns |0⟩ into the plus state and |1⟩ into the minus state.
- H
- the Hadamard gate matrix
- |0⟩
- the basis state 0 (a ket: a state vector)
- |1⟩
- the basis state 1
- |+⟩, |−⟩
- the plus and minus states: equal superpositions with a + or − sign
- Ideal transformer
For an ideal transformer, voltage follows the turns ratio, current varies inversely with turns, and apparent input power equals apparent output power.
Voltage ratio equals turns ratio.
- Vp, Vs
- primary (input) and secondary (output) voltage (volts, V)
- Np, Ns
- number of turns in the primary and secondary winding
Current ratio is the turns ratio flipped.
- Ip, Is
- primary and secondary current (amperes, A)
- Np, Ns
- number of turns in the primary and secondary winding
Power in equals power out: primary volts times amps equal secondary volts times amps.
- Vp, Vs
- primary (input) and secondary (output) voltage (volts, V)
- Ip, Is
- primary and secondary current (amperes, A)
- Inductive reactance
An inductor's opposition to AC current flow, in ohms. It increases as frequency increases; with an inductive load, current lags voltage.
Reactance is 2π times frequency times inductance — so it climbs as frequency rises.
- XL
- inductive reactance (ohms, Ω)
- f
- frequency of the AC signal (hertz, Hz)
- L
- inductance (henrys, H)
- π
- pi, the circle constant (≈ 3.14159)
- Interleaving delay
Delay DSL adds on top of propagation delay — up to 20 ms on ADSL2+.
- Kirchhoff's current law (KCL)
The sum of currents entering a node equals the sum leaving it.
- Kirchhoff's voltage law (KVL)
The algebraic sum of voltage rises and drops around a closed loop is zero — the voltage drops around any loop add up to the source voltage.
- Multimode fiber (MMF)
Fiber with a numerical aperture of about 0.20–0.50: a wider acceptance cone, used over shorter distances.
- Network-powered broadband (NEC 830)
The NEC article for network-powered broadband communications systems — broadband powered from the network side.
- Nonlinear load
A load that does not draw current in proportion to the applied sinusoidal voltage. Its distorted current is a fundamental plus harmonic components; electronic power supplies and rectifier-input loads commonly produce them. Harmonics add current distortion and heating in conductors and transformers, and triplen harmonics in four-wire wye systems can add in the neutral rather than cancel.
Distorted current is the fundamental sine wave plus a stack of harmonics at whole-number multiples of its frequency.
- i(t)
- the instantaneous current at time t (amperes, A)
- t
- time (seconds, s)
- I1
- amplitude of the fundamental (A)
- In
- amplitude of the nth harmonic (A)
- n
- harmonic number
- ω
- angular frequency of the fundamental (radians per second)
- φ1, φn
- phase angle of the fundamental and of the nth harmonic (radians)
- sin
- sine
- Σn=2∞
- sum over the harmonics n = 2, 3, 4, … without end
- Numerical aperture (NA)
A measure of the cone of light a fiber accepts, set by the core and cladding refractive indices. Single-mode fiber: NA ≈ 0.12 — a tight beam, one propagation mode, minimal dispersion. Multimode fiber: NA ≈ 0.20–0.50.
The acceptance of a fiber is the square root of the difference between the squared core and cladding indices.
- NA
- numerical aperture (dimensionless)
- n1
- refractive index of the core
- n2
- refractive index of the cladding
- Ohm's law
The relationship between voltage, current, and resistance in a circuit.
Voltage equals current times resistance.
- V
- voltage (volts, V)
- I
- current (amperes, A)
- R
- resistance (ohms, Ω)
- Optical fiber cables (NEC 770)
The NEC article for optical fiber cables and raceways: fiber backbone, transmission by light.
- Optical network terminal (ONT)
A small device installed at the customer's premises that converts the optical signal to Ethernet; the customer's router connects to the ONT's Ethernet port.
- Optical power budget (OPB)
What the link can afford to lose: transmitter power minus the receiver's minimum. The full end-to-end loss from OLT to ONT must stay within it.
The budget is what the transmitter puts out minus the least the receiver can still read.
- OPB
- optical power budget (dB)
- Ptx
- transmitter power (dBm)
- Prx,min
- the receiver's minimum power (dBm)
Total loss is fiber, splitters, connectors, and splices added up — with the system margin carried as one more line item.
- Ltotal
- total end-to-end loss, OLT to ONT (dB)
- αf
- fiber attenuation (dB/km)
- d
- fiber distance (km)
- Σ ILsplit
- the sum of every splitter's insertion loss (dB)
- Nc
- number of connector pairs
- αc
- connector loss per pair (dB)
- Ns
- number of splices
- αs
- splice loss per joint (dB)
- M
- system margin for ageing and temperature (dB)
- fiber · splitters · connectors · splices · margin
- the labels under the braces, naming each term
- Passive optical network (PON)
A network that uses passive 1:N optical splitters. Each split divides the optical power equally — but the loss in dB does not divide equally: it adds logarithmically.
- Pauli-X gate
The bit flip, or quantum NOT.
Pauli-X swaps the two basis states: |0⟩ becomes |1⟩ and back.
- X
- the Pauli-X gate matrix
- Phase (S) and T gates
Single-qubit gates that leave |0⟩ alone and shift the phase of |1⟩.
S multiplies the |1⟩ part by i (a quarter turn); T by e to the iπ/4 (an eighth turn).
- S
- the phase gate matrix
- T
- the T gate matrix
- i
- the imaginary unit, √−1
- e
- Euler's number, the base of the natural logarithm (≈ 2.718)
- π
- pi, the circle constant (≈ 3.14159)
- Post-quantum cryptography
Lattice-based and hash-based algorithms resistant to Shor's algorithm; standardized by NIST in 2024.
- Power factor
A ratio between 0.0 and 1.0 relating real power to apparent power. A purely resistive AC load has a power factor of 1.0. Where waveform distortion is present, distinguish displacement power factor from true power factor.
- Power triangle
Apparent power (VA), real power (W), and reactive power (VAR) relate like the sides of a right triangle, so reactive power follows from the other two.
Apparent power squared equals real power squared plus reactive power squared.
- S
- apparent power: the total delivered to the circuit (volt-amperes, VA)
- P
- real (active) power: the power doing work (watts, W)
- Q
- reactive power (volt-amperes reactive, VAR)
- Power-limited and fault-managed power cables (NEC 722)
The NEC article for cables for power-limited circuits and fault-managed power circuits — a generic power-limited or fault-managed power cable without a class number.
- Premises-powered broadband (NEC 840)
The NEC article for premises-powered broadband communications systems — customer-side powered optical network equipment.
- Propagation delay
The time a signal takes to cross a span. Light travels through silica fiber at about 2 × 10⁸ m/s — roughly two-thirds of its speed in vacuum — so a 100 km span adds about 0.5 ms one way.
- Quantum Fourier transform (QFT)
The quantum analogue of the discrete Fourier transform and the core subroutine of Shor's algorithm and quantum phase estimation. It runs in O(n²) gates on an n-qubit register, where the classical FFT runs in O(N log N).
The QFT spreads one input state over every output state, each with a phase that turns with x times k.
- |x̃⟩
- the transformed state
- |x⟩
- the input basis state
- |k⟩
- an output basis state
- QFT
- the quantum Fourier transform
- N
- the number of basis states (N = 2ⁿ for n qubits)
- Σk=0N−1
- sum over k from 0 to N − 1
- x, k
- integer labels of the input and output basis states
- e
- Euler's number, the base of the natural logarithm (≈ 2.718)
- i
- the imaginary unit, √−1
- π
- pi, the circle constant (≈ 3.14159)
- Quantum gate
A unitary transformation of qubit states. All quantum gates are unitary matrices.
Undoing a gate is always possible: U-dagger times U gives back the identity.
- U†
- the conjugate transpose of U ("U-dagger")
- U
- a gate's matrix
- I
- the identity matrix
- Quantum interference
Quantum algorithms exploit constructive interference to amplify correct answers and destructive interference to cancel wrong ones.
- Quantum key distribution (QKD)
Key exchange such as the BB84 protocol, in which eavesdropping disturbs the quantum state and so becomes detectable. Commercial deployments exist.
- Qubit
A quantum bit. A classical bit is always 0 or 1; a qubit exists in a superposition of both, weighted by complex probability amplitudes. Measurement collapses the superposition irreversibly.
A qubit's state is a weighted blend of 0 and 1.
- |ψ⟩
- the qubit's state (a ket)
- |0⟩
- the basis state 0 (a ket: a state vector)
- |1⟩
- the basis state 1
- α, β
- complex probability amplitudes of |0⟩ and |1⟩
The two probabilities must add up to one.
- |α|2
- the probability of measuring |0⟩
- |β|2
- the probability of measuring |1⟩
- RMS voltage
For a sinusoidal waveform, the effective AC voltage: the peak voltage divided by √2, about 0.707 of the peak.
RMS is peak over root two — about 0.707 of the peak.
- Vrms
- root-mean-square voltage: the effective AC voltage (volts, V)
- Vpeak
- peak voltage: the maximum amplitude of the waveform (V)
- Series resistance
Resistances in series add directly.
Total series resistance is the sum of the parts.
- Rtotal
- total resistance of the series circuit (ohms, Ω)
- R1, R2, R3
- the individual resistors in series (Ω)
- Shannon–Hartley theorem
The maximum theoretical throughput of a channel, set by its bandwidth and its signal-to-noise ratio. Fiber's near-zero noise floor and multi-THz optical bandwidth give it a theoretical capacity orders of magnitude above copper.
Capacity grows in step with bandwidth, but only with the logarithm of the signal-to-noise ratio.
- C
- channel capacity (bits per second)
- B
- bandwidth (Hz)
- S/N
- signal-to-noise ratio (linear, not dB)
- log2
- base-2 logarithm
- Shor code
A quantum error-correcting code that uses 9 physical qubits per logical qubit and corrects arbitrary single-qubit errors (X, Z, and Y).
- Single-mode fiber (SMF)
Fiber with a 9 µm core that carries a single light mode with virtually no modal dispersion, enabling multi-gigabit speeds over distances exceeding 40 km without amplification.
- Splitter insertion loss
The loss a passive 1:N optical splitter puts on each output. The ideal (theoretical) loss is set by the split ratio alone; real splitters add excess loss from manufacturing imperfections — typically 0.1–0.5 dB for a PLC splitter.
Splitting light N ways costs ten times the base-10 logarithm of N, in dB — 3 dB for every halving.
- ILsplit
- ideal splitting loss of a 1:N splitter (dB)
- N
- split ratio: the number of outputs
- log10
- base-10 logarithm
- dB
- decibels
A real splitter loses the ideal amount plus its excess loss.
- ILactual
- actual insertion loss, excess loss included (dB)
- ILexcess
- excess loss from manufacturing imperfections (dB)
- N
- split ratio: the number of outputs
- log10
- base-10 logarithm
- Three-phase power
The real power of a balanced three-phase load, from line-to-line voltage, line current, and power factor. √3 (≈ 1.732) is the line-to-line multiplier for three-phase systems.
Three-phase power is root three times voltage times current times power factor.
- P
- total three-phase real power (watts, W)
- V
- line-to-line voltage (volts, V)
- I
- line current (amperes, A)
- PF
- power factor, between 0.0 and 1.0
- Total internal reflection
When light strikes the core–cladding boundary at an angle greater than the critical angle, it reflects entirely back into the core with zero energy lost to the cladding — the fundamental mechanism that makes fiber work.
- Twisted pair
Copper wire pairs over which traditional telco infrastructure (DSL, POTS) transmits electrical signals.
LEARNING IN PUBLIC
I'm still studying — the standards, the test gear, and the field itself — and working through continuing education toward my next license renewal. When I learn something worth passing on, it lands here. When a note is wrong, it gets corrected here, in the open; if you spot an error, tell me.
THE FLOW
These are not raw sightings. They are the concrete results of work done under Standards and weighed in Analysis — and the lessons those results taught. What holds is promoted into Research; what fails changes the practice, and in time the Standards themselves.