What Is The Difference Between Cisco Nexus And Catalyst?
Cisco offers a wide range of modular and fixed-configuration switches that help every business find the right solution to their networking needs....
11 min read
Eric Sommers
:
06.16.2025
Ever stood in front of a switch rack with a box of optics and thought, “Wait… is this the right one?” You’re not alone.
Cable type, distance, speed, form-factor, connector, and vendor compatibility — these are just a few of the critical factors that determine which transceiver or cable you actually need. Choosing the right optical transceiver isn’t as simple as grabbing the first one that fits. In fact, transceiver use cases are often one-to-one — meaning only a specific module will work based on your environment.
Take Cisco, for example. There are 17 different 10G SFP+ models. But if you need a short-range, multi-mode, 10G optic with LC ports, you’re probably looking for the SFP-10G-SR.
Whether you’re building out a data center, upgrading enterprise core switches, or just learning the ropes, this guide walks you through the world of optical transceivers — from 1G to 800G. We’ll break down the different types (SFP, QSFP, OSFP), what they’re used for, how to avoid compatibility headaches, and where AOCs and DACs fit into the picture.
And yes — we’ll help you find exactly what you need, without overpaying for OEM optics.
🔎 Want to skip ahead and browse optics by type, speed, form factor, or compatibility?
👉 Use the Optics Finder Tool →
Before diving into form factors and protocols, let’s start with the basics: what is an optical transceiver?
Optical transceivers are hardware components that send and receive data over fiber optic cabling by converting electrical signals into light pulses, and then back again to electrical signals on the other side.
Compared to copper media, Fiber optic cabling can transport data over much longer distances, at much higher speeds, is about half the diameter, and is immune to electrical interference.
Here’s a quick size comparison of SFP and QSFP modules next to a 2.5" hard drive:
If you’ve been doing this a while, you know that optics are more than just a line item in the Bill of Materials (BOM). At OEM pricing, the cost of the transceivers can cost more than the platforms themselves. It's why Gartner Research labeled OEM Optics as “The Biggest Rip Off in Networking.”
Take it from one of our customers — a national logistics company — they saved $2.1 million upgrading just seven facilities to 10G with Edgeium optics. That’s a significant amount of money that will stand up 2-3 other projects for the customer. And the $2.1M savings was for a client who receives a 68% standard channel discount.
No issues. No CLI workarounds. Just instant plug-and-play.
This is where our journey begins! What fiber you put in the walls will dictate what type of fiber module you will need. You can use the cable plant that you can see to determine whether a cable run is single-mode or multi-mode.
Basically, if it's yellow, it's single-mode. If it's any other color, it's multi-mode. As for the type of multi-mode, most vendors are standardizing on the following:
Common types of multi-mode fiber include:
Single-mode fibers have a small core (<10 µm) allowing just one mode of light, ideal for long distances. Multi-mode fibers allow multiple light modes but are more limited in range.
You can't mix and match. If you have single-mode cabling, you need single-mode optics.
Real World Example
We once won a new customer because we shipped transceivers overnight — with Saturday delivery. The client, a healthcare provider, was racing to bring a new site online, and delays weren’t an option. His words? “This is about to become a medical emergency — for me.”
Edgeium came through, and the site went live on time.
📦 Need last-minute gear? We stock nearly $50M in inventory, ready to ship fast — even on weekends. Request a Quote and we'll help you look like a hero!
The difference in performance between single-mode and multi-mode fibers is primarily distance, although power draw can be included. This assumes we’re not comparing OM1 With OS2. OM1, OM2, and even now OM3 are relatively old.
Single-mode fiber allows much further distances as a single mode can easily be more concentrated. So, why not use all single-mode fiber and avoid any gotchas with distance? Cost. Single-mode components are significantly more expensive than their multi-mode counterparts.
*screenshots taken from www.cdw.com on 6/3/2025
Let’s break down the most common types of optics you’ll run into — what they are, what they’re used for, and how to know which ones you need.
There are two main form factors:
Each header below includes a basic use case and real-world applications. You’ll find these transceivers (and more) in Edgeium’s Optics Finder.
Generally:
There are 10 primary versions of the SFP and QSFP form-factors that allow different transmission speeds, and there are various models within each of those categories as well that offer varying connectors, distances, media, etc.
SFP 100mb and 1Gbps transmissions over ethernet, as well as 2G and 4G over Fibre Channel. These modules offer RJ-45 or LC connectors and transmits/receives over a single channel. There are 9 different options differing by distance, media, and 2 that use the fiber strands differently (channel, lane, and path are used interchangeably).
Transceiver |
Max Distance |
Media |
Connectors |
Special Feature |
1000Base-T |
100m |
Copper |
RJ-45 |
|
1000Base -SR |
550m |
MMF |
LC |
|
1000Base -LX |
10km |
SMF |
LC |
|
1000Base -EX |
40km |
SMF |
LC |
|
1000Base -ZX |
80km |
SMF |
LC |
|
1000Base -EZX |
120km |
SMF |
LC |
|
1000Base -XZX |
160km |
SMF |
LC |
|
1000Base -BIDI |
120km |
SMF |
LC |
Bi-directional support |
1000Base -CWDM |
80km |
SMF |
LC |
"Coarse" Wavelength Division Multiplexing |
A quick note on the BiDi and CWDM parts. Both of these use a technology known as Wavelength Division Multiplexing (WDM). WDM allows the transceiver to transmit and receive 2 different wavelengths in opposing directions over 1 fiber effectively doubling the throughput capacity of the transceiver. A 10Gbps WDM transceiver allows 20Gbps of transmission.
SFP+ This is an “enhanced” version of the SFP that supports data rates of 10Gbps, as well as 4G, 8G, and 16G over Fibre Channel. The SFP+ also communicates over a single lane and utilizes LC or RJ-45 connectors.
Transceiver |
Max Distance |
Media |
Connectors |
Special Feature |
10GBase-T |
80m |
Copper |
RJ-45 |
|
10GBase-USR |
100m |
MMF |
LC |
|
10GBase-SR |
300m |
MMF |
LC |
|
10GBase-LRM |
220m |
MMF |
LC |
|
10GBase-LR |
10km |
SMF |
LC |
|
10GBase-ER |
40km |
SMF |
LC |
|
10GBase-ZR |
100km |
SMF |
LC |
|
10GBase-BIDI |
80km |
SMF |
LC |
Bi-directional support |
10GBase-CWDM |
80km |
SMF |
LC |
Coarse Wavelength Division Multiplexing |
SFP28 Also the same physical characteristics as the SFP and SFP+, but with an upgraded electrical interface that can handle 25Gbps per lane over ethernet and 32Gbps over Fibre Channel. All SFP28 transceivers utilize LC connectors.
Transceiver |
Max Distance |
Media |
Connectors |
Special Feature |
25GBase-SR |
100m |
MMF |
LC |
|
10/25GBase-SR |
100m |
MMF |
LC |
Compatible with SFP+ and SFP28 ports |
25GBase-ESR |
400m |
MMF |
LC |
|
10/25GBase-ESR |
400m |
MMF |
LC |
Compatible with SFP+ and SFP28 ports |
25GBase-LR |
10km |
SMF |
LC |
|
10/25GBase-LR |
10km |
SMF |
LC |
Compatible with SFP+ and SFP28 ports |
25GBase-ER |
40km |
SMF |
LC |
|
25GBase-BIDI |
80km |
SMF |
LC |
Bi-directional support |
SFP56 Again, same physical chassis of SFP, but uses PAM4 modulation, and is designed for 50Gbps and 100Gbps connections. While SFP56 are currently only available with LC connectors, look for SFP56 to push copper to 50Gbps!
Transceiver |
Max Distance |
Media |
Connectors |
50GBase-SL |
30m |
MMF |
LC |
50GBase-SR |
100m |
MMF |
LC |
50GBase-LR |
15km |
SMF |
LC |
Modulation is the process of converting data into radio waves. After the light signal is generated, it needs to be modulated, or packaged, with the electrical data signal.
QSFP+ The “Quad” Small Form-Factor Pluggable (QSFP) introduces 4 channels over a single fiber in a slightly larger form-factor.to allow 4x 10Gbps transmission totaling a 40Gbps throughput. The QSFP+ also introduces MPO and MPT connection options. MPO/MPT are capable of bundling multiple fibers in a single connector to support greater throughput.
Transceiver |
Max Distance |
Media |
Connectors |
Special Feature |
40GBase-SR4 |
150m |
MMF |
MPO/MPT |
|
40GBase-ESR4 |
400m |
MMF |
MPO/MPT |
|
40GBase-IR4 |
40km |
SMF |
LC |
|
40GBase-LR4 |
10km |
SMF |
LC |
|
40GBase-SWDM4 |
150m |
MMF |
LC |
|
40GBase-LX4 |
150m/10km |
MMF/SMF |
LC |
|
40GBase-ER4 |
30km |
SMF |
LC |
|
40GBase-BD |
150m |
MMF |
LC |
|
QSFP28 The QSFP28 simply added 4 channels using the SFP28 technology allowing 4x 25Gbps per channel to total 100Gbps throughput capability.
Transceiver |
Max Distance |
Media |
Connectors |
100GBase-SR4 |
100m |
MMF |
MPO/MTP |
100GBase-ESR4 |
300m |
MMF |
MPO/MTP |
100GBase-PSM4 |
2km |
SMF |
MPO/MTP |
100GBase-SWDM4 |
150m |
MMF |
LC |
100GBase-IR4 |
2km |
SMF |
LC |
100GBase-ECWDM |
10km |
SMF |
LC |
100GBase-LR4 |
10km |
SMF |
LC |
100GBase-ER4L |
40km |
SMF |
LC |
100GBase-ZR4 |
80km |
SMF |
LC |
100GBase SL-DR |
500m |
SMF |
LC |
100GBase SL-FR |
2km |
SMF |
LC |
100GBase SL-LR |
10km |
SMF |
LC |
QSFP56 - The QSFP56 is a slightly more complex improvement of the QSFP28 and was designed to support 200Gbps of throughput. The primary change is the modulation technology which uses PAM-4 rather than NRZ. Without going too much into the details, just think of NRZ as having a maximum transmission value of 25Gbps where PAM-4 allows 50Gbps. Rather than 4x25Gbps in the QSFP28, the QSFP56 transmits over 4 independent channels at 50Gbps totaling 200Gbps throughput.
Modulation is the process of converting data into radio waves. After the light signal is generated, it needs to be modulated, or packaged, with the electrical data signal.
Transceiver |
Max Distance |
Media |
Connectors |
Special Feature |
200GBase-SR4 |
100m |
MMF |
MTP/MPO-12 UPC |
4x50G PAM4 |
200GBase-FR4 |
2km |
SMF |
LC |
4x 50G PAM4 |
QSFP112 The QSFP112 pushes throughput capability to 400G. Uses 4 optical pairs, each channel operates at 50Gbps PAM4, resulting in a total of 8 fibers (4x TX and 4x RX). These transceivers can be used to connect a single 400G connection, or break out to 4x100G with a compatible cable.
Transceiver |
Max Distance |
Media |
Connectors |
Special Feature |
400GBase-SR4 |
100m |
MMF |
MTP/MPO-12 APC |
4x100G PAM4 |
400GBase-DR4 |
500m |
MMF |
MTP/MPO-12 APC |
4x 106.25G PAM4 |
QSFP-DD The QSFP-DD brings “double density” to the party. The QSFP-DD is built with an additional row of contacts allowing 4 channels of high-speed transmission up to 100Gbps totaling 400G throughput capability.
Transceiver |
Max Distance |
Media |
Connectors |
Special Feature |
400GBase-SR8 |
100m |
MMF |
MTP/MPO-16 APC |
8x 50G PAM4 |
400GBase-SR4.2 |
150m |
MMF |
MTP/MPO-12 UPC |
8x 50G PAM4 |
400GBase-DR4 |
500m |
SMF |
MTP/MPO-12 APC |
|
400GBase-FR |
2km |
SMF |
MTP/MPO-12 APC |
|
400GBase-LR |
10km |
SMF |
MTP/MPO-12 APC |
|
400GBase-FR4 |
2km |
SMF |
LC Duplex |
|
400GBase-LR4 |
10km |
SMF |
LC Duplex |
|
OSFP The OSFP or Optical Small Form-factor Pluggable doubles the capacity of the QSFP-DD. This transceiver has 8 channels for transmission each capable of 100Gbps totaling 800Gbps throughput capability with development of 200Gbps channels in the works totaling 1.6TB. Some OSFP modules allow a "breakout mode" which enables the transceiver to connect with multiple lower bandwidth applications including QSFP-DD, QSFP56, QSFP28, and even some SFP28 and SFP+ form factors.
Transceiver |
Max Distance |
Media |
Connectors |
Special Feature |
800GBase-SR8 |
100m |
MMF |
2x MPO-12 APC |
8x100G PAM4 |
800GBase-2DR4 |
500m |
SMF |
2x MPO-12 APC |
8x100G PAM4 |
800GBase-2PLR4 |
10km |
SMF |
2x MPO-12 APC |
8x100G PAM4 |
800GBase-2FR4 |
2km |
SMF |
2x LC |
8x100G PAM4 |
800GBase-2LR4 |
10km |
SMF |
2x LC |
8x100G PAM4 |
Compare common optical transceiver types by speed, distance, and where they’re most often deployed
🔎 Want to quickly filter by platform, speed, or form factor?
👉 Use the Optics Finder Tool →
You’ve selected your speed, cable medium, distance, and form factor, and you’re ready to plug and play — right?
Not so fast.
If you’ve ever ordered optics from a third-party vendor only to watch your Cisco switch spit out an ominous “unsupported transceiver” message, you know exactly why coding matters.
Oh, did we tell you that our Optics Finder Tool has compatibility filters as well?
🔎 Use the Optics Finder Tool →
Did you ever wonder why individual transceivers are so expensive but Twinax assemblies aren’t? You’re again not alone.
If you’re running short-distance, high-speed links — especially inside racks or between adjacent switches, servers, etc — Active Optical Cables (AOCs) and Direct Attach Copper (DACs) will yield a significant savings opportunity.
These are pre-terminated cable assemblies that combine optics and cable into one neat plug-and-play package. No fussing with separate modules and fiber at a fraction of the cost of purchasing two individual optics and jumpers to connect them.
These modules use embedded lasers and are available in multiple breakout formats, offering high-speed connections without the need for additional converters.
DACs and AOCs also come in breakout assemblies allowing us to “breakout” a larger connection speed into multiple connections of a smaller speed. Think a single 40G QSFP+ module on one side of the assembly and four 10G SFP+ modules on the other. Or 100G QSFP28 that breaks into four 25G SFP28.
Any of the “QSFP” typically come in breakout options, as such what the “Q” stands for. Those quad lanes are broken into a combination of either 2, 4, or 8 different lanes.
Both are available in breakout configurations — like 100G to 4x25G — and Edgeium offers custom dual-coded cables that can connect two different OEM switches. For example: Arista on one end, Cisco on the other.
📚 Want a full breakdown of when and why to use these?
👉 Explore the AOCs & DACs Page →
OEMs like Cisco, Juniper, and HPE embed code into their gear to ensure transceivers are “correctly” coded. This isn’t about performance — if the coding isn’t right, the transceiver simply won’t work.
Here’s the good news: Edgeium can code custom AOCs and DACs to work across different OEM platforms. Need to connect a Mellanox NIC on one end and a Cisco Nexus chassis on the other? No problem.
If you’re seeing critical alerts tied to CRC errors, start by checking those modules. CRC (Cyclic Redundancy Check) errors usually indicate a layer 1 connectivity issue — corrupted data frames caused by hardware or cabling problems.
Here’s how to troubleshoot:
What is coding?
Every transceiver includes a small EEPROM chip containing metadata. This chip tells your switch who made it, what it does, and whether it’s “authorized.”
Edgeium pre-codes optics for over a dozen major platforms, so your gear just works — no command-line acrobatics, reboots, or guesswork.
Real-World Example
One Edgeium customer was upgrading connections between Nexus 5596 switches and Nutanix servers using Mellanox NICs. Their original VAR quoted them nearly $54,000 — recommending 16 OEM SFP+ transceivers for each side and $45 jumpers in between.
Instead, Edgeium provided 12 custom, dual-coded cables compatible with both Cisco and Mellanox — for just $1,050 total.
👉 That’s the kind of savings that keeps engineers (and budgets) happy.
We’ve helped resolve dozens of costly network issues caused by transceiver missteps. Here are a few hard-earned lessons worth passing on:
We worked with a healthcare client who needed optics shipped overnight to bring a new site online. Unfortunately, once onsite, he grabbed a box of transceivers that had been mislabeled in the data center.
After making several physical connections and seeing no link lights, he began troubleshooting. Turns out, the box marked as single-mode transceivers actually contained multi-mode optics — a mismatch that simply doesn’t work.
Lesson 1: Always match the transceiver type (single-mode or multi-mode) to the fiber cable.
Lesson 2: Double-check the contents of any open box before you travel.
A customer running Cisco gear had always purchased Cisco-branded optics — and had been overpaying for years. When they finally tested Edgeium optics during their first 100GbE deployment, the results were clear.
After a few successful test lab runs, they replaced OEM QSFP-100G-LR-S optics with Edgeium-branded equivalents — saving nearly $300,000. Fully compatible. Lifetime warranty. No failures.
Lesson: Non-OEM transceivers are a reliable, cost-effective alternative to OEM brands.
Optics are engineered for specific distances. Knowing the exact length of your cable run is critical — especially when paths run through buildings, ceilings, or under streets.
One customer deployed SFP-10G-LRM optics on an existing single-mode cable plant, but ran into intermittent packet loss and connection issues. After troubleshooting, they discovered the cable run exceeded the 300-meter spec for LRM optics.
The fix? A simple switch to SFP-10G-LR — and the problems disappeared.
Lesson: Distance matters more than you think.
With OEM optics, you’re often paying for a brand name — not better performance or reliability. It's literally a more expensive sticker on the module.
Edgeium optics are:
We help network engineers across industries reduce costs, simplify purchasing, and get the right optic the first time — whether it’s for a core router or a top-of-rack link in a brand-new data center.
🧰 Not sure what you need?
Use the Optics Finder Tool to search by speed, form factor, platform, and more.
You don’t just need optics that work — you need optics that work and also don’t break your budget.
That’s exactly why engineers and IT leads across data centers, financial firms, healthcare systems, and cloud platforms choose Edgeium.
We take the guesswork out of choosing the right transceiver:
Whether you're upgrading 1G links to 10G, deploying 100G leaf-spine architectures, or sourcing breakout assemblies for 400G core connections, Edgeium has the hardware and the know-how to help you scale smarter.
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