Reference

Glossary

Plain-English definitions for every acronym, term, and product code referenced in NetAPI documentation.

A B C D E F G H I J L M N O P Q R S T V W Z

A

AOC: Active Optical Cable. A factory-terminated cable with optics built into each end. Limited reach (typically up to 30m) but cheaper than a separate transceiver + patch-cord setup.
AOS-S / ArubaOS-S: HPE Aruba's legacy switch operating system (formerly ProVision / Procurve). The CX line uses AOS-CX.
ASIC: Application-Specific Integrated Circuit. The dedicated chip in a switch that handles packet forwarding. Determines what speeds and features the platform supports.
Autoneg: Auto-negotiation. A protocol where two link partners negotiate speed and duplex. Required at some speeds (1G copper), optional at others, increasingly absent at very high speeds (400G+ uses forced configuration).

B

BER: Bit Error Rate. The fraction of bits received in error. Target for typical Ethernet links is better than 1×10⁻¹² (one error in a trillion bits) pre-FEC; with FEC, post-correction BER is typically 1×10⁻¹⁵ or better.
BiDi: Bidirectional. A transceiver that uses different wavelengths for transmit and receive on a single fiber strand, doubling the capacity of a fiber pair. Common at 1G (1310/1490 nm) and 10G (1270/1330 nm).
Bore cap / dust plug: The plastic cover that protects the fiber connector or transceiver port from dust and damage. Always replace when not in use.

C

C-band: The 1530–1565 nm wavelength window. Where DWDM systems and most long-reach (ER, ZR, coherent) modules operate.
Cage: The metal enclosure on the switch that the transceiver inserts into. SFP cages, QSFP cages, OSFP cages, etc.
Catalyst: Cisco's enterprise switch product line (Catalyst 9200, 9300, 9500, etc.). Runs IOS-XE.
CMIS: Common Management Interface Specification. The current standard for the management interface on QSFP-DD, QSFP56, and OSFP modules. Successor to SFF-8636.
Coherent: A class of optical transceivers (typically 100G ZR, 400G ZR, 400G ZR+, 800G ZR) that use phase modulation and DSP-based reception to reach distances of 80–120 km or more on a single channel without amplification.
Connector: The physical interface where fiber meets transceiver. Common types: LC duplex, MPO/MTP (8/12/16-fiber), SC (legacy).
CRC: Cyclic Redundancy Check. A frame integrity check; CRC errors indicate the frame arrived corrupted.
CWDM: Coarse Wavelength-Division Multiplexing. Multiplexing of widely spaced wavelengths (typically 20 nm apart) on a single fiber. Used in 100GBASE-CWDM4 and similar.

D

DAC: Direct Attach Cable. A copper cable with transceiver connectors built into each end. Cheaper than fiber but limited to ~5m for passive, 10m for active variants.
DCI: Data Center Interconnect. A link between two data centers, often long-haul. Drives demand for ER, ZR, and coherent optics.
DDM / DOM: Digital Diagnostics Monitoring / Digital Optical Monitoring. The MSA-defined interface for reading optical health from a transceiver.
dBm: Decibels relative to one milliwatt. The standard unit for optical power. 0 dBm = 1 mW; −3 dBm = 0.5 mW; −10 dBm = 0.1 mW.
DFB laser: Distributed-Feedback laser. A narrow-linewidth laser used in single-mode modules (LR, ER, DWDM). More precise than VCSEL or FP lasers but more expensive.
DR4 / DR8: Data center Reach, parallel single-mode. 400GBASE-DR4 = 4× 100G PAM4 to ~500m; 800GBASE-DR8 = 8 parallel lanes to 500m.
DWDM: Dense Wavelength-Division Multiplexing. Packing 40, 80, or more closely-spaced wavelength channels onto a single fiber in the C-band. Used in long-haul transport networks.

E

EDC: Electronic Dispersion Compensation. DSP-based compensation for fiber dispersion, used in 10GBASE-LRM and some other modules.
EEPROM: Electrically Erasable Programmable Read-Only Memory. The small memory chip in every transceiver that stores its identity, capabilities, and DDM thresholds.
EML laser: Electro-absorption Modulated Laser. A high-performance modulated laser used in higher-speed and longer-reach modules.
EOS: Arista's switch operating system (Extensible Operating System). Linux-based, with a CLI familiar to network engineers from other vendors.
ER / ER4 / ER8: Extended Reach. A reach class supporting up to 40 km on single-mode fiber, typically at 1550 nm or 1310 nm CWDM. 800GBASE-ER8 extends this to 800G.

F

FEC: Forward Error Correction. Error-correcting codes added to the data stream so the receiver can fix bit errors without retransmission. Required at 25G and above. RS-FEC(528,514) at 25G/100G; RS-FEC(544,514) at 200G/400G/800G.
Form factor: The mechanical shape of a transceiver. SFP/SFP+/SFP28 are physically interchangeable; QSFP+/QSFP28 are physically interchangeable; QSFP-DD is mechanically backward-compatible with QSFP28; OSFP is a separate, wider form factor for 400G and 800G.
FR / FR4 / FR8: Forward Reach. A 2 km reach class on single-mode parallel fiber. 400GBASE-FR4, 800GBASE-FR8.

G

Golden unit: A reference module known to perform exactly to spec, used as the validation target during release testing. Every NetAPI SKU is tested against a live golden unit before release.

H

Hot-pluggable / Hot-swap: A module that can be inserted or removed while the switch is powered and running. All MSA-compliant SFP/QSFP/OSFP family modules are hot-pluggable.

I

IOS / IOS-XE / IOS-XR: Cisco's three operating system families. IOS is legacy; IOS-XE is the modern Catalyst/ASR platform; IOS-XR is the carrier-class platform (NCS, ASR9000).

J

Junos: Juniper's switch and router operating system. Used across EX, QFX, MX, SRX, and ACX lines.

L

L-band: The 1565–1625 nm wavelength window. Used by some DWDM systems and high-power long-haul transmissions.
Lane: A single transmit/receive signal pair within a multi-lane module. A 100G QSFP28 has 4 lanes × 25G; a 400G QSFP-DD has 8 lanes × 50G; an 800G OSFP has 8 lanes × 100G PAM4.
Laser bias current: The current required to drive the laser to its operating point. Rises over the laser's lifetime; a rising bias current with stable Tx power indicates aging.
Link budget: The total optical loss a link can tolerate, calculated as Tx power − Rx sensitivity.
LR / LR4 / LR8: Long Reach. A reach class for up to 10 km on single-mode fiber.

M

Meraki: Cisco's cloud-managed switch and security product line. Coding requirements differ from Catalyst/Nexus.
Mode: A path that light can take through optical fiber. Multi-mode fiber supports many modes; single-mode supports only one. More modes → more dispersion → less reach.
MPO / MTP: Multi-fiber Push-On / Mechanical Transfer Push-on. A connector that bundles 8, 12, 16, or 24 fibers into one body. Standard for QSFP/OSFP SR4/SR8 modules and breakout patch panels.
MSA: Multi-Source Agreement. An open specification defining the mechanical, electrical, and management interface of a transceiver. Examples: SFF-8472 (SFP+), SFF-8636 (QSFP28), CMIS (QSFP-DD/OSFP).
Multi-mode fiber: Fiber with a larger core (50 µm or 62.5 µm) that supports multiple light propagation modes. Cheaper but limited reach. Variants: OM1, OM2, OM3, OM4, OM5.

N

Nexus: Cisco's data-center switch product line (Nexus 3000, 7000, 9000). Runs NX-OS.
NX-OS: Cisco's operating system for the Nexus product line.

O

OEM: Original Equipment Manufacturer. In transceiver context, refers to the switch vendor (Cisco, Juniper, etc.) or the OEM module they bundle with the switch.
OS10: Dell's network operating system for the S-series and Z-series data-center switches.
OSFP: Octal Small Form-factor Pluggable. A wider QSFP-class module with 8 electrical lanes. The primary 800G form factor, 8 lanes × 100G PAM4. Not physically backward-compatible with QSFP.

P

PAM4: Pulse Amplitude Modulation, 4 levels. A signaling scheme that encodes 2 bits per symbol (vs. 1 bit per symbol in NRZ). Used at 50G per lane and above. Doubles capacity at the cost of reduced signal-to-noise margin, requiring stronger FEC.
Patch cord / Patch cable: A short fiber cable used to connect a switch to a patch panel, or two patch panels to each other.
PHY: Physical layer transceiver. The block in a switch ASIC (or a separate chip) that drives the SerDes to the optical module.
PSM4: Parallel Single-Mode 4 lanes. A 100G reach class that uses 4 parallel single-mode fibers (vs. CWDM4 which multiplexes 4 wavelengths onto one fiber).

Q

QSFP family: Quad Small Form-factor Pluggable. The family of 4-lane modules. QSFP+ = 40G, QSFP28 = 100G, QSFP56 = 200G, QSFP112 = 400G. QSFP-DD doubles to 8 lanes (400G or 800G).

R

RoHS: Restriction of Hazardous Substances. EU regulation governing materials in electronic products. All NetAPI modules are RoHS compliant.
RS-FEC: Reed-Solomon Forward Error Correction. The standard FEC for 25G, 100G, 400G, and 800G Ethernet. Specific codes: RS(528,514) at 25G/100G, RS(544,514) at 200G/400G/800G.
RU / U: Rack Unit. 1.75 inches of vertical space in a 19-inch equipment rack. Most ToR switches are 1U or 2U.
Rx: Receive. As in "Rx power", the optical power arriving at the receiver photodiode.

S

SerDes: Serializer / Deserializer. The high-speed serial interface inside a switch ASIC that drives the electrical lanes to a transceiver.
SFF: Small Form-factor. The committee within SNIA that produces transceiver MSAs (SFF-8472, SFF-8636, etc.).
SFP: Small Form-factor Pluggable. The original 1G fiber transceiver form factor; subsequent generations (SFP+, SFP28) share the same mechanical envelope at higher speeds.
Single-mode fiber: Fiber with a small core (9 µm) supporting only one propagation mode. Longer reach, more precise lasers required.
SKU: Stock Keeping Unit. A unique product code.
SNMP: Simple Network Management Protocol. Used to poll DDM and other operational data from switches into an NMS.
SR / SR4 / SR8: Short Reach. A multi-mode reach class supporting up to 300m on OM3, 400m on OM4 (per lane). 800GBASE-SR8 reaches 100m on OM4 or 150m on OM5.

T

TAC: Technical Assistance Center. The vendor-side support organization (Cisco TAC, Juniper JTAC, etc.).
Tx: Transmit. As in "Tx power", the optical power launched into the fiber by the transmitter laser.

V

VCSEL: Vertical-Cavity Surface-Emitting Laser. The low-cost laser used in multi-mode transceivers (SR, SR4, SR8). Emits at 850 nm; rugged but limited reach.

W

Wavelength: The "color" of the laser, measured in nanometers (nm). Determines fiber compatibility, reach, and which WDM channels are usable.
WDM: Wavelength-Division Multiplexing. Carrying multiple wavelengths on a single fiber, expanding capacity without pulling more fiber. CWDM and DWDM are variants.

Z

ZR / ZR+: Z-Reach. A long-haul reach class. Traditional ZR is direct-detect at 80 km; 100G/400G/800G coherent ZR uses DSP for 80–120 km without amplification. ZR+ (OpenZR+) extends to several hundred km with amplification.