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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

Fiber Copper
Made up of glass fiber Made up of copper wire
Carries data in the form of light Carries data in the form of electric signals
Offers higher bandwidth Offers lower bandwidth
Transmission speed is faster Transmission speed is slower
Low latency High latency
Installation cost is high Installation cost is less
Attenuation is very low Attenuation is high
Fiber is thin and light, easily breakable Copper is heavier and thick, difficult to break
More resistant to corrosive materials Prone to corrosive materials
More reliable, and durable Less reliable, and durable
Large life span Small life span
Not affected by electrical/magnetic interface Affected by electrical/magnetic interface
More secure – no leakage of light and are difficult to tap Less secure – leakage of signals and easy to tap
No Crosstalk problem problem Prevalent to Crosstalk problem
High noise immunity  Low noise immunity
Charge carriers are photons, which do not carry any charge, so they do not get affected Charge 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.

Type Speed
SFP 1G
SFP+ 10G
SFP28 25G
SFP56 50G
QSFP+ 40G
QSFP28 100G
QSFP56 200G
QSFP-DD 400G
OSFP/QSFP-DD 800G

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.

QSFP28

Industry Standards Mode Distance Connector
QSFP28 Industry Standards Mode Distance Connector
100GBASE-SR4 IEEE 802.3bm, QSFP28 MSA, SFF-8665, SFF-8636, RoHS, CPRI, eCPRI MMF 100 m MTP/MPO-12
100GBASE-SR10 IEEE 802.3ba MMF 150m MTP/MPO-24
100GBASE-LR4 IEEE 802.3ba 100GBASE-LR4, IEEE 802.3bm, QSFP28 MSA, SFF-8665, SFF-8636 SMF 10km LC Duplex
100GBASE-ER4 IEEE 802.3ba, QSFP28 MSA Compliant SMF 40km MTP/MPO-12
100GBASE-ZR4 QSFP28 MSA Compliant SMF 80km LC Duplex
100GBASE-DR IEEE 802.3cd 100GBASE-DR Specification compliant SMF 500m LC Duplex
100GBASE-FR 100G Lambda MSA 100G-FR Specification compliant SMF 2km LC Duplex
100GBASE-LR 100G Lambda MSA 100G-LR Specification compliant SMF 10km LC Duplex
100GBASE-PSM4 100G PSM4, QSFP28 MSA Compliant SMF 500m MTP/MPO-12
100GBASE-CWDM4 IEEE 802.3ba, IEEE 802.3bm, SFF-8665, SFF-8636, 100G CWDM4 MSA, QSFP28 MSA SMF 2km LC Duplex
100GBASE-4WDM QSFP28 MSA Compliant SMF 10km LC Duplex
100GBASE-DWDM IEEE 802.3bm, QSFP28 MSA, SFF-8636, SFF-8024 SMF 80km CS Duplex
100GBASE-BiDi QSFP28 MSA Compliant SMF 20km LC Simplex
100G CLR4 100G CLR4 Industry Alliance SMF 2km CS 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.

Rate Technology Breakout Capable Electric Lanes Optical Lanes
10G SFP+ No 10G 10G
25G SFP28 No 25G 25G
40G QSFP+ Yes 4x 10G 4x10G, 2x20G
50G SFP56 No 50G 50G
100G QSFP28 Yes 4x 25G 100G, 4x25G, 2x50G
200G QSFP56 Yes 4x 50G 4x50G
2x100G QSFP28-DD Yes 2x (4x25G) 2x (4x25G)
400G QSFP56-DD Yes 8x 50G 4x 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.

Conclusion

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.

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Everything You Need to Know About Network Link Optics

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