Tag Archives: GLC-SX-MMD

Connect Cisco Catalyst 3750 Series Switches to Network

Cisco Catalyst 3750 series switches are widely used in today’s access layer of the network, which can provide Ethernet speed of Gigabit. There are a variety of configurations in this series of Cisco switches. They can fit different applications and offering forward data rates from 32G to 128G by using Cisco StackWise technology. It is an economical solution to many midsize enterprises and office. However, to make full use of these switches, how to connect them to network becomes very important. This post will illustrate Cisco Catalyst 3750 series switches connection in details.

cisco catalyst 3750 and optics

Do You Know Cisco Catalyst Series Switches?

The ports on switches decide what types of connectors and cables can be connected with the switches. Thus, let’s get a close look at Cisco Catalyst 3750 switches ports details first. As mentioned, one of the biggest advantages is that Cisco Catalyst 3750 can support Cisco StackWise technology. Up to nice physical Catalyst 3750 switches can be interconnected into one logical switch with a high performance of 32G or 128G. This is largely depending on the StackWise ports on the rear panel of the switch as shown in the following picture.

Cisco Catalyst 3750G-48TS rear panel

Another great advantage of Cisco Catalyst 3750 switch is its great flexibility and adaptability owning to its various configurations. The Ethernet ports of Cisco Catalyst 3750 can support data rage from 10M to 1G. For instance, or example, Cisco Catalyst 3750G-12S contains 12 SFP ports, Cisco Catalyst 3750G-24TS-1U has 24 Ethernet 10/100/1000 ports plus 4 SFP uplinks in 1 rack unit (RU) height, Cisco Catalyst 3750G-48PS is armed with 48 Ethernet 10/100/1000 ports with IEEE 802.3af PoE and 4 SFP uplinks. The following picture shows the detailed ports information of Cisco Catalyst 3750G-48TS, which has 48 Ethernet 10/100/1000 ports and 4 SFP uplinks.

Cisco Catalyst 3750G-48TS front panel

Connecting Cisco Catalyst 3750 Series Switch to Network

There are mainly two types of ports on Cisco Catalyst 3750 switches: RJ45 and SFP. Different cables and connectors are used to connect the switches to network. The following will offer detailed information about how to connect these ports.

Cisco Catalyst 3750 Switch 10/100/1000 Ports Connection

10/100/1000 Ports on Cisco Catalyst 3750 are RJ45 ports, which should be connected with copper cables (as shown in the following picture). For different applications, the cable types are also different. For example, when connecting Cisco Catalyst 3750 to workstation, servers, router, the straight-through cables are suggested to use with RJ45 connector. When it the switch is connected to repeaters, crossover cable is recommended. When connecting to 1000Base-T-compatible devices, be sure to use a twisted four-pair, Cat5 cable.

Cisco Catalyst 3750 RJ45 connection
Cisco Catalyst 3750 Switch SFP Module Ports Connection

Most Cisco Catalyst 3750 switches have several SFP ports on their front panel. They can support Gigabit Ethernet, by using SFP modules related. Both copper and fiber optic links can be built with these ports and SFP modules. If connected with fiber optic 1000Base-LX or 1000Base-SX SFP modules a link supporting Gigabit Ethernet based on fiber optic can be built. If connected with copper SFP module like 1000Base-T, a copper link will be built. The following picture illustrates the connections with fiber optic SFP module port and Copper SFP module port from left to right separately.

Cisco catalyst 3750 SFP port connection

Cabling Solution for Cisco Catalyst 3750 Series Switches

More related cables and modules that Cisco Catalyst 3750 switches supporting are listed in the following chart for your reference.

Port Type
Data Rate
Connectors/Modules & Cables
RJ45 Ports 10BASE-T ports  RJ-45 connectors, two-pair Cat 3, 4, or 5 unshielded twisted-pair (UTP)
10BASE-T PoE ports  RJ-45 connectors, two-pair Cat 3, 4, or 5 UTP cabling power pins 1, 2 (negative) and 3, 6 (positive)
100BASE-TX ports  RJ-45 connectors, two-pair Cat 5 UTP
100BASE-TX PoE ports  RJ-45 connectors, two-pair Cat 5 UTP, power on pins 1, 2 (negative) and 3, 6 (positive)
SFP Ports 100M GLC-GE-100FX LC duplex, MMF
GLC-FE-100LX LC duplex, SMF
GLC-FE-100BX-D LC simplex, SMF
1G GLC-SX-MM LC duplex, MMF
GLC-BX-U LC simplex, SMF
GLC-T RJ-45, Cat 5

All the above mentioned products are fully tested in FS.COM Test Center. Please contact sales@fs.com for more details.

Do You Know Digital Diagnostic Monitoring?

Cisco announced the end of sale of its SFP transceiver Cisco GLC-SX-MM transceiver and published a replacement—Cisco GLC-SX-MMD transceiver in 2012. The module numbers of the two transceiver only differ in one letter “D”. This “D” mainly represents a function of Cisco GLC-SX-MMD transceiver and is inherited by most of optical transceivers offered today. It is the main reason why Cisco GLC-SX-MMD transceiver can replace its predecessor. What is this “D”? Why the GLC-SX-MMD can replace GLC-SX-MM? MMD-digital diagnostic monitoring will be introduced in this article.

What Is Digital Diagnostic Monitoring (DDM)?

“D” in GLC-SX-MMD represents the DDM function which is short for digital diagnostic monitoring according to the industry standard MSA (Multi-Source Agreement) SFF-8472 and is also known as DOM (Digital Optical Monitoring). When buy fiber optic transceiver today, you will have the option with or without DDM/DOM. And most of the modern transceivers are with the DDM function. This technology allows the user to monitor real-time parameters of the fiber optic transceivers, like optical input/output power, temperature, laser bias current, and transceiver supply voltage, etc.

What Can Digital Diagnostic Monitoring Do?

Literally, DDM function can provide component monitoring on transceiver applications in details. However, DDM’s application is not limited to this. The SFF-8472 added DDM interface and outlined that DDM interface is an extension of the serial ID interface defined in GBIC specification, as well as the SFP MSA. DDM interface includes a system of alarm and warning flags which alert the host system when particular operating parameters are outside of a factory set normal operating. Thus, DDM interface can also enable the end user with the capabilities of fault isolation and failure prediction. This part is to illustrate what can be done with DDM.

Component Monitoring: The DDM enables the end user to monitor key parameters in the performance of the fiber optic transceiver including the following:

  • Transceiver temperature
  • Transceiver supply voltage
  • Laser bias current
  • Transmit average optical power
  • Received optical modulation amplitude (OMA) or Average Optical Power

The real-time diagnostic parameters can be monitored to alert the system when the transceiver’s specified operating limits are exceeded and compliance cannot be ensured.The following picture shows the eye diagram illustrating optical figures of merit.

Digital diagnostic monitoring eye diagram

Fault isolation: The DDM function can be used to isolate the particular location of fault in fiber optic network system. Combining the DDM interface status flags, transceiver hard pins and diagnostic parametric monitor data, the specific location and cause of a link failure can be pinpointed.

Failure prediction: The DDM can also be used to help in failure prediction on fiber optic links, which is based on the transceiver parametric performance. Although, this application is not yet fully mature, but there is still room for improvement. There are two basic types of failure conditions that can be seen on fiber optic transceivers:

  • Device faults—A device non-operation or malfunction. Typically applied more to transmitter performance, due to nature of semiconductor lasers.
  • High error rate conditions—Operating conditions are such that transceiver is operating at its signal-to-noise limit. Applies more to fiber optic receiver performance.

Providing parameter monitoring, fault isolation, and failure prediction, fiber optic transceivers with DDM help to ensure that the business can be proactive in preventative maintenance of the network and ensure business continuity. And it would easy to explain why modern transceivers are with DDM and why GLC-SX-MMD can replace GLC-SX-MM. It is irresistible development trend of industry and technology.

What should be mentioned is that although optical transceivers with DDM are much popular than those without DDM, some user still use the older optical transceivers in consideration of the upgrading costs. To satisfy the customers’ needs, optical transceivers with DDM and without DDM are provided by the vendors like Fiberstore.

Related Article: Cable and Optics Solution for Catalyst 4948E and Catalyst 4948E-F Switches