Category: Fiber Transceivers

Optical transceivers, Active Optic Cables, data center switches, and cable management in data centers.

What should know Before Selecting CWDM SFP Transceivers

As an extension of wavelength division multiplexing (WDM), coarse wavelength division multiplexing (CWDM) is a technology that multiplexes a number of optical carrier signals onto a single optical fiber through the use of different wavelengths (i.e., colors) of laser light. A CWDM SFP (Small Form-factor Pluggable) transceiver is a hot-swappable input/output device that plugs into an SFP port or slot of a switch or router, linking the port with the fiber-optic network. It is a  kind of optical-electric/electric-optical converter. With the transmitter on one end, the CWDM SFP transceiver takes in and converts the electrical signal into light, after the optical fiber transmission in the fiber cable plant, the receiver end again converts the light signal into electrical signal. The following figure shows the CWDM SFP transceiver in the CWDM system. In the figure, TX represents “transmit”, RX represents “receive”. Being a kind of compact optical transceiver, CWDM SFP transceiver is widely used in optical communications for both telecommunication and data communication. It is designed for operations in Metro Access Rings and Point-to-Point networks using Synchronous Optical Network (SONET), SDH (Synchronous Digital Hierarchy), Gigabit Ethernet and Fibre Channel networking equipment.
Three Components of CWDM SFP Transceivers
The CWDM SFP transceiver consists of an un-cooled CWDM Distributed Feed Back (DFB) laser transmitter, a PIN photodiode integrated with a Trans-impedance Preamplifier (TIA) and a Microprogrammed Control Unit (MCU). The DFB laser used in the CWDM SFP transceiver transmitter is a 18 CWDM DFB wavelengths laser. It is well suited for high capacity reverse traffic. Obeying the standard diode equation for low frequency signals, The PIN photodiode has a 80km transmission distance. And the MCU is a high-speed, executive, input-output (I/O) processor and interrupt handler for the NRL Signal Processing Element (SPE).
Advantages of CWDM SFP transceivers
Using existing fiber connections efficiently through the adoption of active wavelength multiplexing, CWDM SFP transceivers have improved the designs of telecommunications devices and other technologies. Here are some advantages of CWDM SFP transceivers:
Scalability and Flexibility—CWDM SFP transceivers can support multiple channels. It means that more channels can be activated as demand increases. CWDM SFP transceivers have a wide variety of network configurations that range from the meshed-ring configurations to the multi-channel point-to-point. In point-to-point configurations, the two endpoints will connect directly through a fiber link, allowing users to add or delete as many as eight channels at a time.
Low Risks in Investment—Most CDWM SFP transceivers have a low failure rate, which is less likely to be the reason why the user’s solution fails. It helps enterprises increase the bandwidth of the Gigabit Ethernet optical infrastructure without adding any additional fiber strands and can also be used in conjunction with other SFP devices on the same platform. Thus the user will be able to re-invest the capital saved by avoiding prematurely failed devices.
Selecting a Right CWDM SFP Transceiver
There are many kinds of CWDM SFP transceivers in the market. Their wavelengths are available from 1270 nm to 1610 nm, with each step 20 nm. Different CDWM SFP transceivers have different color codes, distances, date rates and laser operating wavelengths. For example, the CWDM-SFP-1470, which is colored gray, is one of Cisco CWDM SFP. It is a CWDM SFP transceiver that rates for distances up to 80 km and a maximum bandwidth of 1Gbps, operating at 1470nm wavelength. Customers may choose a CWDM SFP transceiver in accordance with their actual needs.
Applied to the access layer of Metropolitan Area Network (MAN), CWDM is a low-cost WDM transmission technology. fiber-mart.com provides the aforesaid CWDM-SFP-1470 and other types of CWDM SFP transceivers, which are convenient and cost-effective solution for the adoption of Gigabit Ethernet and Fibre Channel in campus, data center, and metropolitan-area access networks.

the Features & Applications of Cisco 6500 Series Switches

As modular chassis network switches, the Cisco catalyst 6500 series switches are optimized choices for network investment protection for enterprises and service providers. It delivers high security, resiliency, and port density for data center, LAN and WAN. Cisco 6500 series switches was researched and developed from 1999, and now they have been widely used in campus, data center and some large size enterprises. This article would mainly talk about their features and applications.
Cisco Catalyst 6500 series switches provide multiple slot choices—3-, 6-, 9-, 9-Vertical and 13-slot of different chassis. They offer the broadest range of interface modules with industry-leading performance and advanced feature integration. Catalyst 6500 Series switches feature an unparalleled range of integrated services modules, including multi-gigabit network security, content switching, telephony, and network analysis modules. There are five available 6500 series switch models in total, which would be mainly presented in the following.
Features & Benefits
—High security
The 6500 Series switches integrate proven, multi-gigabit Cisco security solutions, including intrusion detection, firewall, VPN, and Secure Sockets Layer (SSL) into existing networks.
—High scalability
They provide up to 400-mpps performance with distributed forwarding architecture.
—High flexibility
By integrating advanced services such as security, wireless LAN services, customers would experience the the widest range of interfaces and densities, from 10/100 and 10/100/1000 Ethernet to 10 Gigabit, and from DS-0 to OC-48, and performs in any deployment from end to end.
—Operational Consistency
A common set of modules are shared among all chassis configurations, and any network management tool can be used in the network.
—Time-saving
With Cisco IOS Software Modularity and platform, power supply, supervisor engine, switch fabric, and integrated network services redundancy. They deliver applications and services continuity in a converged network, minimizing disruption of mission-critical data and services, which offer the maximum network uptime to save your time.
—Network investment protection
The Cisco 6500 series provides extraordinary investment protection for your network, for they support three generations of interchangeable, hot-swappable modules in the same chassis, optimizing IT infrastructure usage, maximizing ROI, and reducing TCO.
Applications of Cisco 6500 Series Switches
The Cisco 6500 series switches are mainly deployed in campus networks, metro edge, Internet service provider (ISP) and grid computer networks. Owing to time and space limiting, we would only clarify the first two in this passage.
Campus Networks
As we mentioned in the first paragraph, the Cisco 6500 series switches have been widely applied to campus network. The 10/100 and 10/100/1000 autosensing modules provide inline power for the wiring closet. Besides, they are equipped with the work-class networking software and 1/10 Gigabit interface modules, which feature as robust high-availability, security and manageability. All in all, that would be of high performance for your distribution and core network in campus.
Metro Edge
The Cisco 6500 switches provide point-to-point and multipoint Ethernet services, which is rather suitable for metro and intermetro network deployments. It has edge, distribution, and core network-layer interfaces, which is compliant with Network Equipment Building Standards (NEBS). They offer high performance 10 Gigabit Ethernet uplinks that is of security, availability, and manageability.
Cisco Catalyst 6509-E Switch
As one of Cisco 6500 series switches, Cisco Catalyst 6509-E switch is of eye-catching recently. The 9-slot Cisco Catalyst 6509-E Switch provides high port densities that are ideal for many wiring closet, distribution, and core network as well as data center deployments. It supports1G and 10G Gigabit Ethernet network connection, along with 386 1G SFP ports and 32 10G XENPAK/X2 ports respectively. There are four compatible 1000BASE transceivers in total for the 6509-E switch, 1000BASE-LX/LH SFP, 1000BASE-SX SFP, 1000BASE-T SFP and 1000BASE-ZX SFP. You can plug any of the four transceiver types into the SFP port on this switch to make 1G network connection. The 6509-E supports 10G X2/XENPAK ports, you could connect 10GBase LR X2 module or any other compatible X2/XENPAK modules to the switch.
Conclusion
Cisco Catalyst 6500 Series switches are inevitable choices for network investment of Multigigabit Ethernet services. They feature as high security, scalability, flexibility, operational consistency, time-saving, and network investment protection. Nowadays, they have been deployed in campus networks, metro edge, ISP and grid computer networks.

comparison between CWDM and DWDM

CWDM, just as DWDM, use multiple light wavelengths to transmit signals over a single optical fiber. However, there are still some differences betwwen the two techologies in many ways.
CWDM uses a 20-nm wavelength spacing that is much wider than the 0.4 nm for DWDM. The wider wavelength spacing in CWDM means lower product development costs. This is one reason why CWDM is less costly than DWDM.
Most CWDM devices operate in the 1470-nm to 1610-nm range. The frequency grid for DWDM and the wavelength grid for CWDM systems are defined by the international telecommunication union (ITU) standard G.694.1 and G.694.2, respectively.
CWDM provides a maximum of 8 lambadas between two CWDM multiplexers over a single fiber pair as compared to DWDM Multiplexers, which support up to 32 lambdas (based on 0.8-nm or 100-GHz wavelength spacing) over a single fiber pair. some long-haul DWDM systems can support up to 160 lambdas per fiber pair.
Each CWDM channels uses a specialized gigabit interface converter (GBIC) or small form-factor pluggable (SFP) transceivers are commonly known as colored GBIC and SFP. Each CWDM channels uses a different “color” GBIC or SFP because each lambda represents a different color in the spectrum. In this case, the native GBIC or SFP in the client devices are substituted with a colored GBIC or SFP.
CWDM multiplexers are usually passive (i.e, not powered) devices containing a very accurate prism to multiplex eight separate wavelengths of light along a single fiber pair. And passive CWDM devices cannot generate or repeat optical signals.
No amplification is possible with CWDM because CWDM uses wavelengths that cannot be amplified with EDFA amplifiers. Therefore, the maximum distance for a CWDM link is approximately 100 km.
The Cisco ONS 15501 EDFA, which has a wavelength range of 1530 nm to 1563 nm, can only amplify two signals (1530 nm and 1550 nm) out of the eight signals that are multiplexed onto the fiber pair.
CWDM provides an alternative solution to DWDM for low-latency and high-bandwidth requirements associated with synchronous replication application. However, DWDM is more scalable than CWDM. DWDM also has a longer distance capacity than CWDM because DWDM can be amplified. The main benefit of CWDM is its low cost. It is a cheaper solution than DWDM. In other words, CWDM is optimized for cost, while DWDM is optimized for bandwidth. For enterprises that have access to dark fiber and have only limited scalability requirement, CWDM is a relatively inexpensive way to achieve low-latency and high-bandwidth interconnections between DCs. The CWDM implementation also results in less complex installation, configuration, and operation as compared to DWDM.
CWDM can be deployed in point-to-point, linear, or fiber protected ring topologies, It is limited to a distance of up to 120 km for Gigabit Ethernet and 100 km for 2-G FC in a point -to-point topology. It is typically used only for extension of the FC fabric in a metro or campus application. As CWDM carries only eight lambdas on a single fiber pair, there are limits to the number of possible drops and the number of sites that can be interconnected. A ring or linear topology reduces the distance depending on the number of OADMs traversed by the CWDM channels because each CWDM OADM introduces additional power loss in the network.
CWDM can also be used to enable multiple ISL connections between the switches over a single fiber since it requires less fiber for interconnecting two metro sites. The same benefit applies to port channel implementation between the switches.
In short, DWDM is a solution that provides a higher number of connections and longer reach, or extension, at a much higher cost while CWDM is a more cost-effective solution for metro or campus solutions where the distance is limited.

Something about Optical Circulator

by http://www.fiber-mart.com

The utilization of optical circulator starts from the 1990s, and now it has become one of the important elements in advanced optical communication systems. Similar to the function of an electronic circulator, an optical circulator is used to separate optical signals that travel in opposite directions in an optical fiber. Optical circulator has been widely applied to different fields, such as telecom, medical and imaging industries. Are you ready to know more about this optical device? This article will take you to explore the secrets of optical circulator.
What Is Optical Circulator?
An optical circulator is built to pass light from one optical fiber to another. It is a non-reciprocal device routing the light based upon the direction of light propagation. Both optical circulator and optical isolator can be used to move light forward. However, there is typically more loss of light energy in the optical isolator than in the optical circulator. Optical circulator usually consists three ports: two ports are used as input ports and one port as output port. A signal is transmitted from port 1 to port 2, and another signal is transmitted from port 2 to port 3. Finally a third signal can be transmitted from port 3 to port 1. Many applications only require two, so they can be built to block any light that hits the third port.
Technologies of Optical Circulator Components
An optical circulator includes the components of Faraday rotator, birefringent crystal, waveplate, and beam displacer. The Faraday rotator uses the Faraday effect, which is a phenomenon that the polarization plane of an electromagnetic (light) wave is rotated in a material under a magnetic field applied parallel to the propagation direction of the lightwave. The light propagation in the birefringent crystal depends on the polarization state of the light beam and the relative orientation of the crystal. The polarization of the beam can be changed or the beam can be split into two beams with orthogonal polarization states. Waveplate and beam displacer are two different forms of birefringent crystal. A waveplate can be made by cutting a birefringent crystal to a particular orientation so that the optic axis of the crystal is in the incident plane and is parallel to the crystal boundary. Beam displacer is used to split an incoming beam into two beams with orthogonal polarization states.
Categories of Optical Circulator
According to polarization, optical circulator can be divided into polarization-dependent optical circulator and polarization-independent optical circulator. The former is used for the light with a particular polarization state, and the latter is not restricted to the polarization state of a light. Most of the optical circulators employed in fiber optic communications are designed to be polarization-independent.
According to functionality, optical circulator can be classified into full circulator and quasi-circulator. As mentioned before, full circulator makes full use of all ports in a complete circle. Light passes through from port 1 to port 2, port 2 to port 3, and port 3 back to port 1. About quasi-circulator, light passes through all ports sequentially but light from the last port is lost and cannot be transmitted back to the first port. For most applications, a quasi-circulator is enough.
Conclusion
From this article, you may have a basic impression about optical circulator. It is an efficient and economical solution to use optical circulator for directing light signal with minimum loss. If you are interested in the optical circulator products, welcome to visit fiber-mart.com for more information.

Different Ports on WDM Mux/Demux

In the WDM (wavelength-division multiplexing) system, CWDM (coarse wavelength-division multiplexing) and DWDM (dense wavelength-division multiplexing) Mux/Demux (multiplexer/demultiplexer) modules are often deployed to join multiple wavelengths onto a single fiber. Multiplexer is for combining signals together, while demultiplexer is for splitting signals apart. On a WDM Mux/Demux, there are many kinds of ports for different applications. This article will discuss the functions of these ports on WDM Mux/Demux.
Necessary Ports on WDM Mux/Demux
Channel port and line port are the necessary ports to support the basic function of WDM Mux/Demux to join or split signals in the data network.
Channel Port
A WDM Mux/Demux usually has several channel ports on different wavelengths. Each channel port works for a specific wavelength. Since there are 18 wavelengths of CWDM ranging from 1270 nm to 1610 nm with a 20nm interval, the number of channel ports on CWDM Mux/Demux also ranges from 2 to 18. DWDM has a more dense wavelength spacing of 0.8 nm (100 GHz) or 0.4 nm (50 GHz) ranging from S-Band to L-Band around 1490 nm to 1610 nm. The number of DWDM Mux/Demux channel ports is about 4 to 96 for high-density networks.
Line Port
Each WDM Mux/Demux will have a line port connecting to the network backbone. Combined channels are transmitted or received at the line port. In addition, line port can be divided into dual-fiber and single-fiber types. Dual-fiber line port is used for bidirectional transmission, therefore the transmit and receive port in each duplex channel must support the same wavelength. However, single-fiber line port only supports one direction data flow, thus the transmit and receive port of duplex channel will support different wavelengths. The wavelengths’ order of single-fiber WDM MUX/DEMUX should be reversed at both sides of the network.
Special Ports on WDM Mux/Demux
Apart from the necessary ports, some special ports can also be found on WDM Mux/Demux for particular needs.
1310nm Port and 1550nm Port
1310nm and 1550nm ports are certain wavelength ports. Since a lot of optical transceivers use these two wavelengths for long-haul network, adding these two ports when the device does not include these wavelengths is very important. CWDM Mux/Demux can add either type of wavelength ports, but the wavelengths which are 0 to 40 nm higher or lower than 1310 nm or 1550 nm cannot be added to the device. However, DWDM Mux/Demux can only add 1310nm port.
Expansion Port
Expansion port can be added on both CWDM and DWDM Mux/Demux modules. This is a special port to increase the number of available channels carried in the network. That is to say, when a WDM Mux/Demux can not meet all the wavelength needs, it is necessary to use the expansion port to add different wavelengths by connecting to another WDM Mux/Demux’s line port.
Monitor Port
Monitor port is used for signal monitoring or testing. Network administrators will connect this port to the measurement or monitoring equipment to inspect whether the signal is running normally without interrupting the existing network.
Conclusion
From this post, we can know that a WDM Mux/Demux has multiple types of ports. Channel and line ports are integral ports for normal operation of the WDM Mux/Demux. 1310nm port, 1510nm port, expansion port and monitor port are used for special requests of the WDM application. Hence, you should have a thorough consideration of your project before choosing the WDM Mux/Demux module.

Choose Duplex Fiber or MPO/MTP Fiber for 40G Solutions?

by http://www.fiber-mart.com

There’s been a lot of talk lately surrounding bidirectional 40 Gb/s duplex applications, or BiDi for short. Currently offered as a solution by Cisco®, BiDi runs over duplex OM3 or OM4 multimode fiber using QSFP modules and wavelength division multiplexing (WDM) technology. It features two 20 Gb/s channels, each transmitting and receiving simultaneously over two wavelengths on a single fiber strand – one direction transmitting in the 832 to 868 nanometer (nm) wavelength range and the other receiving in the 882 to 918 nm wavelength range. Avago Technologies also offers a similar QSFP BiDi transceiver.
Unidirectional 40 Gb/s duplex fiber solutions are available from Arista and Juniper. These differ from the BiDi solution in that they combine four 10 Gb/s channels at different wavelengths – 1270, 1290, 1310, and 1330 nm – over a duplex LC connector using OM3 or OM4 multimode or singlemode fiber. These unidirectional solutions are not interoperable with BiDi solutions because they use different WDM technology and operate within different wavelength ranges.
While some of the transceivers used with these 40 Gb/s duplex fiber solutions are compliant with QSFP specifications and based on the IEEE 40GBASE- LR4 standard, there are currently no existing industry standards for 40 Gb/s duplex fiber applications using multiple wavelengths over multimode fiber – either bidirectional or unidirectional. There are standards-based 40 Gb/s applications over duplex singlemode fiber using WDM technology, but standards-based 40 Gb/s and 100 Gb/s applications over multimode use multi-fiber MPO/MTP connectors and parallel optics (40GBASE-SR4 and 100GBASE-SR4).
40 Gb/s duplex fiber solutions are promoted as offering reduced cost and installation time for quick migration to 40 Gb/s applications due to the ability to reuse the existing duplex 10 Gb/s fiber infrastructure for 40 Gb/s without having to implement MPO/MTP solutions. However, some of the concerns surrounding these non-standards based 40 Gb/s duplex fiber solutions include:
Lack of standards compliance and lack of interoperability with standards-based fiber solutions
Risk of being locked into a sole-sourced/proprietary solution that may have limited future support
BiDi and other 40 Gb/s duplex transceivers require significantly more power than standards-based solutions
Lack of application assurance due to operation outside of the optimal OM3/OM4 wavelength of 850 nm
Limited operating temperature range compared to standards-based solutions
Due to the aforementioned risks and limitations of using non-standards-based 40 Gb/s duplex fiber solutions, we recommends following industry standards and deploying 40GBASE-SR4 for 40 Gb/s applications today. While this standard requires multiple fibers using an MPO/MTP-based solution, it offers complete application assurance and interoperability, as well as overall lower power consumption.
Furthermore, TIA and IEC standards development is currently underway for wideband multimode fiber (WBMMF), which is expected to result in a new fiber type (potentially OM5 or OM4WB) that expands the capacity of multimode fiber over a wider range of wavelengths to support WDM technology. While not set in stone, the wavelengths being discussed within TIA working groups are 850, 880, 910, and 940 nm.
Unlike current 40 Gb/s duplex fiber applications, WBMMF will be a standards-based, interoperable technology that will be backwards compatible with existing OM4 fiber applications. WBMMF is expected to support unidirectional duplex 100 Gb/s fiber links using 25 Gb/s channels on 4 different wavelengths. WBMMF will also support 400 Gb/s using 25 Gb/s channels on 4 different wavelengths over 8 fibers, enabling existing MPO/MTP connectivity to be leveraged for seamless migration from current standards-based 40 Gb/s and 100 Gb/s applications to future standards-based 400 Gb/s applications.