Author Archives: Camilla.Zhang

How to Troubleshoot Transceiver and Switch Port Through Loopback Test?

Loopback

Loopback is a commonly used term in telecommunications. It refers to the process of transmitting electronic signals or digital data streams and returning to their sending point without any intentional processing or modification. Therefore, by comparing transmitting signals with the receiving signals, the loopback test is used to debug physical connection problems. But what a loopback test means for fiber optic network and how to make use of it will be the issues that we will explore in this post.

Why Need Fiber Loopback Test?

To conduct a fiber loopback test, the communication devices will be involved, like the transceivers and the switch. As you know, the transceiver is the basic component of fiber optic communication network equipment. We can take the transceiver as a case. Conventionally, a transceiver has a transmitting port and a receiving port, in that way, the loopback test can be applied to test the ports to diagnose whether the transceiver is working well and the configuration of the switch is right. For its unique working mode, the test is a convenient way to maintain transceivers. In the next part, we will deliver how to do the fiber loopback test on the transceiver.

How to Conduct Loopback Test?

In this part, we will introduce two types of tests to troubleshoot transceiver and switch port: single-port test and dual-port test.

Tools You Need to Prepare

To perform tests, things you need to prepare are listed below:

  • Transceivers (2pcs), such as 10G SFP+ SR transceiver.
  • Simplex fiber cable (1 pc).
  • Switch (1 pc), like Cisco switch.
  • Duplex fiber cable (1 pc).
  • Two loopback cables (optional), like LC or SC loopback cable. To know more about loopback cable, you can move to the article: What Is Loopback Cable And How to Use It?
Loopback Cable

Figure 1: Loopback Cable

Loopback Test Steps
Single-port Loopback Test
Single-port Loopback Test

Figure 2: Single-port Loopback Test

1. Connect your transceiver with one simplex fiber cable or loopback cable, such as LC fiber cable or LC loopback cable. At this step, you can examine whether the port and transceiver parameters are normal.

2. Check the software version of the switch.

3. Review the interfaces status to confirm the working status of all ports on the switch.

Display the Working Status of All Ports

Figure 3: Display the Working Status of All Ports

4. Check the working status of the port you are connecting, such as the port 50 in the following figure.

Working Status of Interface 50

Figure 4: Working Status of Interface 50

5. Go over the DDM information to review whether the transceiver works in normal status.

DDM Information of Port 50

Figure 5: DDM Information of Port 50

Dual-port Loopback Test
Dual-port Loopback Test

Figure 6: Dual-port Loopback Test

1. Connect two transceivers with one duplex fiber cable or two loopback cables. At this step, you can examine whether the port and transceiver data rate are matching as well as the link is normal or not.

2. Check the interfaces status to confirm the working status of all ports on the switch.

Ports Working Status Display

Figure 7: Ports Working Status Display

3. Check the working status of the two ports you are connecting, such as the ports 50 and 52 in the following figure.

Working Status of Interfaces 50 and 52

Figure 8: Working Status of Interfaces 50 and 52

4. Go over the DDM information to review whether the transceiver works in normal status.

DDM Information of Ports 50 and 52

Figure 9: DDM Information of Ports 50 and 52

Summary

To troubleshoot the circuit connectivity as well as the transceiver and the switch port, loopback test is a cost-effective way. In this post, we have an overview of loopback and make a demonstration of how to conduct the loopback test on a switch to debug the transceiver and the switch port.

FMT 4000E for DWDM Network Solution

In the network era, the demand for greater traffic capacity, higher bandwidth, and better performance over longer transmission distance have never stopped. Under such a context, the optic transport network (OTN) has undergone great changes to survive. At the moment, FS provides their all-in-one dense wavelength division multiplexing (DWDM) OTN solutions. In this post, we will share one of the most popular DWDM solutions: FMT 4000E.

DWDM Network Basics

DWDM

Dense wavelength division multiplexing is a technology based on wavelength-division multiplexing (WDM). It combines or multiplexes data signals from different sources for transmissions over a single fiber optic cable. At the same time, data streams are completely separated. Each signal is carried on a separate light wavelength. In most cases, the dense wavelength division multiplexing technology is applied in metropolitan network.

Optical Transport Network

Defined by the ITU Telecommunication Standardization Sector (ITU-T), OTN is a set of optical network elements (ONE) that are connected by optical fiber links. Sometimes, it’s also called the digital wrapper technology which provides an efficient and globally accepted way to multiplex different services onto optical light paths. This technology provides support for optical networking by using WDM unlike its predecessor SONET/SDH. It’s able to create a transparent, hierarchical network designed for use on both WDM and time division multiplexing (TDM) devices. The OTN is able to support functions, like transport, multiplexing, switching, management, supervision, and builds OTN client (e.g. SONET/SDH, IP, ATM) connections in the Metro and Core networks.

Optical Transport Network

Figure 1: Optical Transport Network

DWDM Network

The DWDM based network refers to a kind of dense wavelength division multiplexing technology based OTN solution. Compared with CWDM, the DWDM uses more sophisticated electronics and photonics, which makes its transmitting channel are narrower than CWDM channels. Therefore, for a DWDM network, it can support more channels and separate wavelengths (up to 80 wavelengths). It can transmit data in IP, ATM, SONET, SDH, and Ethernet. For it’s protocol and bitrate independent, the DWDM-based OTN networks can carry different types of traffic at different speeds over an optical channel.

DWDM vs CWDM Wavelength

Figure 2: DWDM vs CWDM Wavelength

FMT 4000E for DWDM Solution

In order to make the DWDM OTN deployment easier, FS has launched the high integration FMT WDM transport networks, such as FMT 1800 and FMT 9600E. In this post, we will mainly introduce the most popular solution: FMT 4000E.

What Is FMT 4000E

The FMT 4000E is a device that combines the OTN switching and dense wavelength division multiplexing features and provides unified transmission of all services. It integrates DWDM equipment with OTN function cards (EDFA, DCM, OEO) in a 4U form factor. With FMT 4000E, you can extend the optical link power budget for building long-distance dense wavelength division multiplexing solutions.

FMS 4000E

Figure 3: FMT 4000E

Strengths of FMT 4000E
  • Supports up to 40 wavelengths via the dual fiber bi-directional transmission mode.
  • Transmits up to 100 km with DWDM SFP+ 80km at the rate of 10Gbps.
  • Optional function cards to meet various needs (WDM Mux/Demux, EDFA, DCM, OEO).
  • Dual AC or DC pluggable power supply and fan unit.
  • Supports SDH/SONET, PDH, Ethernet, SAN, LAN, video service transport.
  • Scales easily for the ring, end to end and mesh networks.
  • Suitable for the enterprise, medical, Storage Area Networks (SANs), data centers, campus optical network and video surveillance.
  • Scalable solution for customers to expand capacity as needed. And operating costs and vital resources are greatly saved.
  • Ensure the maximum bandwidth for the required capacity and transmission distances.
  • Fully managed, configured and monitored remotely via FS.COM intelligent network management unit.
  • Simple installation, operation, and maintenance.
  • Standards-based and can integrate with third-party solutions.
  • The solution can be customized to suit specified customer application requirements.
Solution Topology
FMS 4000E Solution Topology

Figure 4: FMT 4000E Solution Topology

Note: This solution does not come with OPM, OPD, OLP, OSW card.

Matching Products
  • 40CH C21-C60 DWDM Mux Card ( 2pcs)
  • 40CH C21-C60 DWDM Demux Card ( 2pcs)
  • 20dB Gain Pre-Amplifier DWDM EDFA Card (2pcs)
  • 17dB Output Booster EDFA Card (2pcs)
  • 40km Passive Dispersion Compensation Card (4pcs)
  • FMT 4U Managed Chassis (2pcs)
  • LC/UPC Single Mode Fixed Fiber Optic Attenuator, 3dB (1pc)

Summary

Obsessed with higher bandwidth applications and the simplest operation, the OTN has broken through its traditional operation and make inroads into the highly integrated OTN. Undoubtedly, the DWDM solution will be the one having the last laugh after networking ups and downs. To share that last laugh, FS provides its DWDM solutions for multi-service optical transport over ultra-long distance: FS WDM Multi-service Transport (FMT) series. They help our customers to build an access transport network with more flexible service access, easier operation, and lower OPEX.