FluxLight GLC-LH-SMD Application: 1Gbps Campus Interconnect with DDM

The GLC-LH-SMD optical transceiver is ideal for trunking light-to-medium access/aggregation switch traffic on campus networks. This transceiver supports full-duplex 1Gbps transmission over up to 10 kilometers (~6.2 miles) of standard single-mode fiber. While many new access switches support 10Gbps uplinks, lower priced options, like the Cisco Catalyst 9200 product featured in this example, are available at 1Gbps. In this application, traffic aggregated at several Catalyst 9200 switches is redundantly trunked to Cisco Nexus 9396PX core switches.

CORE SWITCH: Cisco Nexus 9396PX

Cisco Nexus 9396PX

The Nexus® 9396PX platform is part of the latest generation of the fixed Nexus® 9000 Series Switches. Cisco uses the phrase “Application Centric Infrastructure (ACI)” to describe the technology on which this series is based. The primary elements of ACI are,

  • Automated IT workflows to shorten application deployment
  • Software Defined Networking (SDN)
  • Advanced security and analytics
  • Seamless application migration across multiple locations

The Cisco Nexus 9396PX Switch is a 2RU switch that supports 1.92 Tbps of throughput. The switch includes 48 SFP+ slots which may be equipped with either SFP or SFP+ modules so both 1G and 10G speeds are possible on a per port basis. 12 fixed QSFP uplink slots are included in the N9372PX. These may be equipped with up to 12 QSFP+ 40GE modules or up to 4 QSFP28 100G modules.

The N9396PX may be equipped with a wide range of optical transceiver interface types across the many rates mentioned above. The tables below include the compatible transceiver types for the two categories of ports in the switch.

Table 1 SFP Optical Transceivers

GLC-SX-MMD SFP SX, 550m/OM2, MMF, duplex LC
GLC-LH-SMD SFP LX, 10km, SMF, duplex LC
GLC-EX-SMD SFP EX, 40km, SMF, duplex LC
GLC-ZX-SMD SFP ZX, 70km, SMF, duplex LC
GLC-TE SFP T, 100m, CAT5e, RJ45
GLC-BX-U, GLC-BX-D SFP BX, 10km/40km/80km, SMF, simplex LC


Table 2 SFP+/SFP28 Optical Transceivers

SFP-10G-SR SFP+ SR, 300m/OM3, 400m/OM4, duplex LC
SFP-10G-LR SFP+ LR, 10km, SMF, duplex LC
SFP-10G-LRM SFP+ LRM, 220 OM1 MMF, duplex LC
SFP-10G-ER  SFP+ ER, 40km, SMF, duplex LC
SFP-10G-ZR SFP+ ZR, 80km, SMF, duplex LC
SFP-10G-T SFP+ T, 30m, CAT7, RJ45
SFP-10GBX-UD-PAIR SFP+ BX, 10km, SMF, simplex LC


SFP+ BX, 40km, SMF, simplex LC


Table 3 QSFP+ 40G Optical Transceivers

QSFP-40G-SR4 QSFP+ 40G SR4, 100m, OM3 MMF, MPO connector
QSFP-40G-CSR4 QSFP+ 40G CSR4, 300m OM3 MMF, MPO connector
WSP-Q40GLR4L QSFP+ 40G LR4L, 2Km SMF, duplex LC
QSFP-40G-ER4 QSFP+ 40G ER4, 40Km SMF, duplex LC
QSFP-40G-SR-BD QSFP+ 40G Bidirectional MMF, 100m OM3, duplex LC
QSFP-40G-LR4 QSFP+ 40G LR4, 10km SMF, duplex LC


ACCESS SWITCH:  Cisco Catalyst C9200L-24P-4G

Cisco Catalyst C9200L-24P-4G
Cisco Catalyst 9200 (C9200-24P-4G is the top unit)

Cisco’s Catalyst 9200 series is available in both fixed and modular configurations. The specific model in this example is the C9200-24P-4G. The switch includes 24 POE RJ45 ports and 4 SFP 1GbE slots. The unit may be stacked with other fixed configuration 9200 series models with up to 80 Gbps of stacking bandwidth. The switching capacity is 104 Gbps with a forwarding rate of 154.76 million packets per second (Mpps). Highlights of the Cisco IOS XE software are,

  • Automated device provisioning
  • API-driven configuration
  • Granular visibility (new-real-time network monitoring)
  • Seamless software upgrades and patching

The table below shows the range of optical transceivers that may be equipped in the C9200L-24P-4G’s 4 SFP slots.

Table 4 SFP Optical Transceivers

GLC-SX-MMD SFP SX, 550m/OM2, MMF, duplex LC
GLC-LH-SMD SFP LX, 10km, SMF, duplex LC
GLC-EX-SMD SFP EX, 40km, SMF, duplex LC
GLC-ZX-SMD SFP ZX, 70km, SMF, duplex LC
GLC-TE SFP T, 100m, CAT5e, RJ45
GLC-BX-U, GLC-BX-D SFP BX, 10km/40km/80km, SMF, simplex LC



FluxLight GLC-LH-MD

FluxLight’s GLC-LH-SMD (click link for datasheet) is a Cisco® compatible 1000Base-LX SFP DDM Optical Transceiver and is factory pre-programmed with all the necessary configuration data for fully compatible operation with all Cisco equipment offering SFP slots. The FluxLight GLC-LH-SMD includes a dual-LC connector and supports full duplex 1GbE over up to 10km single-mode fiber links.

FluxLight’s device performs identically to Cisco® original transceivers, are 100% compatible and support full hot swappable operation. The GLC-LH-SMD is 100% MSA (Multi-Source Agreement) compliant, see: SFP MSA.

The major difference between the GLC-LH-SMD and the GLC-LH-SM is the addition of Digital Diagnostics Monitoring, DDM (also known as Digital Optical Monitoring or DOM) as defined in SFF-8472. DDM allows users to locally or remotely monitor the status of critical operating information in the optical transceiver. Monitored status includes current operation temperature, optical transmit power (dBm), optical receive power (dBm), internal supply voltage (Vdc) and transmit bias current. Along with real-time values for each of these parameters, upper and lower thresholds for both Alarm and Warning levels for each are stored in the module’s internal EEPROM.



The GLC-LH-SMD modules equipped in the Cisco Nexus 9396PX and Catalyst C9200 switches offer a duplex LC type connector and utilize single mode fiber (SMF) for transmission. Since this application involves transmission over outside plant fiber across a campus, the optical transceiver modules are typically connected to a nearby optical patch panel using a short single mode jumper cable. An example jumper, shown in the figure above, has dual-LC connectors at each end and is 2 meters long.  If the fiber patch panel is further away or has a connector type other that dual-LC, of course an alternative cables are available, see: FluxLight OS2 fiber jumpers.

Putting it all together

The local network connectivity is achieved by inserting a FluxLight GLC-LH-SMD into each switch and then using an appropriate length Duplex-LC SMF jumper cable to attach to a port on the patch panel, as shown below.

GLC-LH-SMD Application-03

To create a robust network, each C9200 access switch is dual-homed to two Nexus 9396PX switches. Two FluxLight GLC-LH-SMD modules are equipped in the C9200 switches as shown in the diagram below. Since there are three C9200 switches in the example, a total of three GLC-LH-SM modules must be equipped in each of the N9372 switches.

GLC-LH-SMD Application-02

Cisco switches were used to demonstrate the application. FluxLight carries 1000BASE-LX modules compatible with a wide range of OEM switches. Some popular models are listed below.

Table 5 SFP Optical Transceivers for Popular Switch OEMs

E1MG-LX-OM Brocade-Foundry
MA-SFP-1GB-LX Meraki
320-2879 Dell


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