December 24, 2022
Kasinath Rajendran

Everything You Need to Know About Network Link Optics

Optical communication networks are, literally, the backbones of the information superhighway. They have been providing the conduits over which broadband data is delivered worldwide, at the actual speed of light. Hundreds of millions of miles of deployed optical fiber interconnect continents, nations, cities, neighborhoods, and private homes. Behind this backbone comes a suite of complementary optical subsystem components that are pivotal to the operation and management of these networks. These optical microsystems directly interact with the optical signal and – through functionality afforded by design – are able to filter, switch, attenuate, and adapt the optical communication channels carried by the network.

One of the major optical microsystem applications is the optical transceiver. In simple words, an optical transceiver is a device that converts data to light and vice versa to be transmitted and received across optical fibers. Imagine these devices to be traffic merge points in an interstate highway system that takes in off-highway city traffic and links them into super-speed highway traffic. Just as the proper functioning of traffic merges is necessary for the seamless functioning of a highway system, continuous observability of thousands of these devices at scale becomes a must-have for network administrators.

In this blog, we will demystify optical transceiver-based link optics from an engineering perspective. Besides that, we will also highlight the ways Aviz ONES is leveraged by network teams to continuously observe, investigate and triage in real-time, thereby alleviating their time, cost, and resource burdens.

Optical Transceiver – Engineer’s Definition

An Optical transceiver is used to convert electrical signals to optical light signals and optical signals to electrical signals. It is a hot-swappable device that can be plugged into a networking device that can send and receive data. Optical transceivers come in different forms and dimensions called Form Factors which support different speeds and distances. Data center networks can be copper-based connections, fiber-based connections, or a combination of copper and fiber cables called hybrid connections, and transceivers can receive and transmit data in both copper and fiber optic cables.

Why Fiber over Copper

Made up of glass fiberMade up of copper wire
Carries data in the form of lightCarries data in the form of electric signals
Offers higher bandwidthOffers lower bandwidth
Transmission speed is fasterTransmission speed is slower
Low latencyHigh latency
Installation cost is highInstallation cost is less
Attenuation is very lowAttenuation is high
Fiber is thin and light, easily breakableCopper is heavier and thick, difficult to break
More resistant to corrosive materialsProne to corrosive materials
More reliable, and durableLess reliable, and durable
Large life spanSmall life span
Not affected by electrical/magnetic interfaceAffected by electrical/magnetic interface
More secure – no leakage of light and are difficult to tapLess secure – leakage of signals and easy to tap
No Crosstalk problem problemPrevalent to Crosstalk problem
High noise immunity Low noise immunity
Charge carriers are photons, which do not carry any charge, so they do not get affectedCharge carriers are electrons, which carry a negative charge, so they get affected when they move in a wire

Standard Form Factors

The form factor states the physical dimensions of a transceiver which varies in size and shape depending on the speeds and protocols supported. Optical transceiver manufacturers design optics according to the Multisource Agreement (MSA). This is a standard for ensuring that the same form-factor transceivers from different vendors are compatible in size and function for interoperability with different vendor optics.


SFP – Small Form-factor Pluggable

QSFP – Quad Small Form-factor Pluggable

QSFP-DD – Quad Small Form Factor Pluggable Double Density

OSFP – Octal Small Form-factor Pluggable

Transceiver Standards are based on the speed of the optics. Let’s take 100G transceivers that have different form factors CFP, CFP2, CFP4, CXP, and QSFP28. QSFP28 is the newest version of the 100G Optical transceiver. QSFP28 is a widely used 100G transceiver because of its high performance, lower power consumption, and higher density.

QSFP28Industry StandardsModeDistanceConnector
QSFP28Industry StandardsModeDistanceConnector
100GBASE-SR4IEEE 802.3bm, QSFP28 MSA, SFF-8665, SFF-8636, RoHS, CPRI, eCPRIMMF100 mMTP/MPO-12
100GBASE-SR10IEEE 802.3baMMF150mMTP/MPO-24
100GBASE-LR4IEEE 802.3ba 100GBASE-LR4, IEEE 802.3bm, QSFP28 MSA, SFF-8665, SFF-8636SMF10kmLC Duplex
100GBASE-ER4IEEE 802.3ba, QSFP28 MSA CompliantSMF40kmMTP/MPO-12
100GBASE-ZR4QSFP28 MSA CompliantSMF80kmLC Duplex
100GBASE-DRIEEE 802.3cd 100GBASE-DR Specification compliantSMF500mLC Duplex
100GBASE-FR100G Lambda MSA 100G-FR Specification compliantSMF2kmLC Duplex
100GBASE-LR100G Lambda MSA 100G-LR Specification compliantSMF10kmLC Duplex
100GBASE-PSM4100G PSM4, QSFP28 MSA CompliantSMF500mMTP/MPO-12
100GBASE-CWDM4IEEE 802.3ba, IEEE 802.3bm, SFF-8665, SFF-8636, 100G CWDM4 MSA, QSFP28 MSASMF2kmLC Duplex
100GBASE-4WDMQSFP28 MSA CompliantSMF10kmLC Duplex
100GBASE-DWDMIEEE 802.3bm, QSFP28 MSA, SFF-8636, SFF-8024SMF80kmCS Duplex
100GBASE-BiDiQSFP28 MSA CompliantSMF20kmLC Simplex
100G CLR4100G CLR4 Industry AllianceSMF2kmCS Duplex

SR – Short Range

LR – Long Range

ER – Extended Range

ZR – Ze Best Range

LRM – Long Reach Multimode

PSM – Parallel Single Mode Fiber

WDM – Wavelength division multiplexing

CWDM – Coarse wavelength division multiplexing

DWDM – Dense wavelength division multiplexing

BiDi – Bidirectional optical transceiver

The Fanout

A high-speed port is broken into multiple low-speed ports are called Breakout Ports or Breakout cables. For example, a switch with a 400G port can be connected to 4x100G ports using breakout cables. Breakout cables are also called “fanout” cables.

RateTechnologyBreakout CapableElectric LanesOptical Lanes
40GQSFP+Yes4x 10G4x10G, 2x20G
100GQSFP28Yes4x 25G100G, 4x25G, 2x50G
200GQSFP56Yes4x 50G4x50G
2x100GQSFP28-DDYes2x (4x25G)2x (4x25G)
400GQSFP56-DDYes8x 50G4x 100G, 8x50G

Aviz ONES & The Optical Transceiver

Open Networking Enterprise Suite (ONES) is a network management and support application that offers the industry’s only multi-vendor, a multi-NOS solution that delivers Orchestration, Visibility, and Assurance – enabling SONiC adoption in new or existing deployments. ONES consumes telemetry from switches running SONIC, and other NOSs such as NVIDIA Cumulus Linux, Arista EOS, or Cisco NX-OS, and delivers deep insights into the link optics with information on

  • Inventory metrics for speed, type, breakout, lanes, manufacturer, etc.
  • Health metrics based on Digital Optical Monitoring (DOM) telemetry, an industry standard to access operating parameters of transceivers such as Tx Power, Rx Power, Temperature, Supply Voltage, Laser Bias Current, and much more.

This information is collected across any platform and the data is normalized to provide a unified view of the network fabric. ONES provides critical information on faulty transceivers in the fabric with drilled-down capabilities to identify the root cause of failures. An example of how deep ONES can go in terms of providing visibility for optics inventory and operational health is below.


Link availability is critical for any network operations, as the failure of a network link is the primary source of customer-impacting issues in the majority of cases. Hence, optics telemetry monitoring is a must-have in data center monitoring solutions to (a) understand link issues due to transient or permanent failures and (b) proactively identify the optics that are likely to fail and fix them ahead of time. Aviz ONES provides deep insights into optics to achieve the above goals. The optics data collected by ONES can also be extremely useful in qualifying optics before purchase decisions are made. Contact us to learn more about how Aviz can help with Optics Monitoring for your SONiC network.