Multimode fiber has been highly favored by Ethernet users and gained the widest acceptance in network backbones where it has offered users the opportunity to extend link distances, increase network reliability, and lower costs by centralizing electronics. OM3 fiber emerges just at the right time. The predominance of OM3 fiber is that utilizes laser-optimized fiber, which is the highest-capacity medium for short-wave 10G optical transmission. OM4 fiber just joined multimode fiber family after OM3 fiber in order to meet the requirement of longer range applications. This passage would give a brief introduction to OM3 and OM4 fiber, give a further analysis on their differences and selection guide, as well as list their applications.

Both OM3 and OM4 fiber meet the ISO 11801 standard. The standard specifies that OM3 fibers are capable of 10 Gb/s performance over distances of up to 300m. Like being mentioned, the laser optimized 50/125 mm multimode OM3 fiber is of predominance, which provides sufficient bandwidth to support 10 GbE and beyond with cable lengths up to 550 meters. OM4 fiber is a further improvement to OM3 fiber. It also uses a 50µm core but it supports 10 Gigabit Ethernet at lengths up 550 meters and it supports 100 Gigabit Ethernet at lengths up to 150 meters.

Attenuation is caused by losses in light through the passive components, such as cables, cable splices, and connectors. Attenuation is the reduction in power of the light signal as it is transmitted (dB). The maximum attenuation of OM3 and OM4 fiber allowed at 850nm: OM3<3.5 dB/Km; OM4 <3.0 dB/Km. So it is obvious that OM4 fiber causes lower losses due to different construction.

As is known to most people, modal dispersion attaches great importance to bandwidth. The lower the modal dispersion, the higher the modal bandwidth and the greater the amount of information that can be transmitted. The minimum OM3 and OM4 fiber cable bandwidth at 850nm: OM3 2000 MHz·km; OM4 4700 MHz· km. The higher bandwidth available in OM4 means a smaller modal dispersion and thus allows the cable links to be longer or allows for higher losses through more mated connectors.

The maximum transmission distance of OM4 fiber is 400-550m (depending on module capability) while OM3 fiber can only be up to 300m. And thus, OM4 can tolerate a higher level of loss at distances between 200-300m as it is designed to operate at longer distances than OM3 fiber. It may be a more flexible option for network managers to install OM4 fiber within these instances. You can check difference between OM3 and OM4 in transmission distance in the following table.

In comparison to OM3 fiber, the cost for OM4 is higher due to the manufacture process and market fluctuations. In a large extent, cost depends on the construction type of the cable (loose tube, tight buffered, etc.). OM4 fiber cable is about twice as expensive as OM3 fiber cable. This means that the cost difference of lots of fiber products such as standard fiber patch panels, MTP cassette modules, fiber patch cords is very small (as the volume of cable is small).

Fifty micron OM3 fiber is designed to accommodate 10 Gigabit Ethernet up to 300 meters, and OM4 can accommodate it up to 550 meters. Therefore, many users are now choosing OM3 and OM4 over the other glass types. In fact, nearly 80% of 50 micron fiber sold is OM3 or OM4. If you require higher data rates or plan on upgrading your network in the near future, laser optimized 50 micron (OM3 or OM4) would be the logical choice. Compared to OM4, OM3 fiber is more future proofing for most applications, which allows speeds of 10 GB/s up to 100 GB/s. OM4 fiber provides users a transmission solution over longer distances and leaves more wiggle room in optical budgets.

OM3 and OM4 fiber cables are typically used in data center structured cabling environments running high speeds of 10G or even 40 or 100 Gigabit Ethernet, SAN (Storage Area Networking), Fiber Channel, FCOE (Fiber Channel Over Ethernet) with such manufacturers as Cisco, Brocade, EMC and others. Typical applications could be virtualized or internal cloud core data center applications. For 40G and 100G fiber cable applications, MTP/MPO cable would also be a great choice. MTP cabling assemblies (MTP/MPO trunk cable, MTP/MPO harness cable, MTP/MPO conversion cable, etc), with their overwhelming advantages, providing a fast, simple and economical upgrade path from 10 Gigabit to 40 or 100 Gigabit applications.

In this article, we mainly discussed OM3 fiber, OM4 fiber, their main differences, transmission guide and applications for 10G/40G/100G network. We put emphasis on OM3 and OM4 fiber 10G/40G/100G transmission distance and selection guide. OM3 and OM4 multimode fiber provide a cost effective solution for inside buildings or corporate campuses. Hope this article would be helpful for you to understand OM3 and OM4 fiber and to select right fiber cable for yourself.

Oznake: OM3 Fiber, OM4 Fiber, multimode fiber

As a worldwide leader in IT and fiber optical networking, Cisco switches play a leading role in manufacturing network switches and in providing switching solutions for data center and enterprise networks with large and medium-size forms. MikroTik, a Latvian company which was founded in 1996 to develop routers and wireless ISP systems. Their cloud switches are highly favored by many Ethernet users in recent years. And thus, people are entangled with Cisco and Mikrotik switches. This article would give brief introduction to Cisco and Mikrotik switches, and put emphasis on Mikrotik Switches Vs Cisco Switches.

According to different usage, Cisco divided their switches into the following categories: LAN Access Switches, LAN Digital Building Switches, LAN Core and Distribution Switches, Data Center Switches, Service Provider Switches, Industrial Ethernet Switches, Virtual Networking and Small Business Switches. And every category has its switching series. The Cisco Catalyst series switch delivers ease of management and configuration for small to medium-sized enterprise wiring closets in a single system, without the need for additional modules. The following list is about the Cisco Catalyst series switch.

Comparing to Cisco switches, the total amount of Mikrotik switches is much smaller. According to the official website of Mikrotik, there are only twelve Mikrotik switches. Ethernet smart switches and cloud core router switches are two series switches of Mikrotik switches. The cloud core switch, or cloud router switch, abbreviated as CRS, is a highly configurable switch, powered by RouterOS. They are the new products of Mokrotik switches. For the cloud router switch, there are nine models currently available. Here lists three different cases of the cloud core switch:

• CRS125-24G-1S-2HnD-IN (integrated wireless, indoor case)


• CRS125-24G-1S-IN (indoor case)


• CRS125-24G-1S-RM (rackmount case)

The CPU on both Cisco and Mikrotik switches is used for management purposes (snmp stats, cli management, etc) and it does not affect the data path. Switching is not done in CPU, neither on Cisco nor on Mikrotik. Switching is done on dedicated ASIC chips specifically designed for this job (thus giving wirespeed). So comparing the CPUs won't mean much about forwarding performance - which is the metric you should care about.

One of big problems with Mikrotik switches is their power. The buyers would prefer to pay another couple hundred dollars to have dual power supplies that are removable. And thus, many Ethernet users cannot use Mikrotik in these cases. Comparing to Mikrotik switches, Cisco switches have less power consumption by their advanced technology.

Most network monitoring software systems natively understand, support and auto-detect Cisco devices and support Cisco SNMP OIDs (CPU, temp, load, bandwidth, errors, power supply status, and many other sub-system counters in a Cisco device.

When configuring your existing network monitor system(s), your network monitor system(s) may not even know what a Mikrotik is and probably does not have native built-in MIBs/OIDs used by SNMP to auto-check/monitor a network. Thus, an administrator would probably need to configure the Mikrotik graphic icons and configure all of the SNMP checks for MIBs/OIDs from/to a Mikrotik.

Mikrotik routers and switches are great. Most people like them and use them almost everywhere. However, because Mikrotik is still the new kid on the block when it comes to carrier-grade commercial-grade business grade high-throughput products, it may sometimes be a little difficult to find local network technicians or local phone support for Mikrotik products when adding new equipment into your network. So Cisco switch is more solid and people are more satisfied with them.

Oznake: network switch, core switch, ethernet switches

25G Ethernet and 40G Ethernet are two “transiting” approaches for upgrading network from 10G to 100G. Some analysts believe 25G could be the second highest Ethernet server connectivity technology sold and shipped in the next five years, behind 10G. Meanwhile, a number of comments from industry experts declaring that 40G Ethernet is dead. Is that true? And how to make a right decision? This passage would give a brief introduction on 25G switch and 40G switch and put emphasis on 25G switch Vs. 40G switch.

25G technology is the new standard that offer significant density, cost and power benefits for server to top of rack connections. Its single higher speed 25 Gb/s lanes maximize bandwidth and switch fabric utilization. A single lane per physical port maximizes the number of connected servers or uplinks per switch. Generally, 25G switch is a 48 port switch on the 25G switch market right now. Nowadays, many major brands of switch manufactures have launched their 25G switch, such as Cisco, Juniper, Arista, Mellanox, Dell.

Comparing with 25G switch, 40G switch is much familiar to us. A 40G switch generally refers to the data speeds of the ports feeding into the switch. Hence, a 40G switch has 40 Gb/s ports. The overall switching capacity of the 40G switch will be much higher depending on the total number of ports and the power of the switching fabric itself. According to Infonetics Research in early 2015, 40G switch has been popular in the data center market while 100G switch is more popular with service providers. And thus, 40G Ethernet and 40G switch are not so dead like being mentioned in the fast paragraph.

Relatively speaking, 25G switch is less common on the market. In terms of 25G switch compatibility, that is depending the switch supplier. Just take Arista 25G switch for an example, the majority of their 25G switches and Network Interface cards offer backward compatibility to 10G, there is the flexibility to manage a gradual migration to higher speed servers and mix and match port speeds. All SFP based 25G ports on Arista switches and 25G NICs from Cavium can be used at 10G speed. The compatibility of 40G switch also depends on the switch brands. But as a new emerging technology, 25G switch has higher compatibility than 40G switch.

High performance 25GbE chips use single-lane 25G serializer-deserializer (Serdes) technology similar in operation to 10GbE but delivering 2.5 times the performance, thus reducing the power and cost per gigabit significantly. 25G provides higher port and system density than a comparable 40G solution. Both power savings and higher density results in lower cooling requirements and operational expenditure for data center operators.

Switch-to-server or switch-to-switch (or switch-to-blade switch) are two connection options for 25G switch connection. Right now, network vendors are positioning 25G only for switch-to-server. Until now, no network vendor advertising 25G for switch-to-switch—Cisco doesn’t even offer a 25G fiber transceiver, and HPE has priced theirs higher than 40G and 100G transceivers. In other words, no one is talking about 25G for switch-to-switch links right now. We shall see this in 2018.

25G twinax works best within a single rack with a top-of-rack switch and 1 and 2 meter cables. 25G with 3+ meter cables requires forward error correction (FEC), which adds ~250ns of one-way latency and may introduce vendor interop issues. If you’re adopting 25G, plan to densely pack compute into 10kVA–12kVA racks. 40G DAC cable is more expensive than 25G DAC cable based on the identical cable length.

Through the above description and comparison, we are cleared about some pros and cons of 25Gb Ethernet switch and 40Gb Ethernet switch as well as their main differences. As for how to choose the best one, that depends on your demand and usage environment. 25G switch uses less power and produce less heat than 40G, but it is limited at 25G distance. For data center network connectivity, 100G switch is more of a smart choice than 25G switch and 40G switch. In campus and access networks with their long fiber runs and low bandwidth needs, 40G switch is more worthy to buy. So far it seems that 25G switch is not a cost-effective solution.

Oznake: 25G switch, 40gb ethernet switch, 48 port switch