Category: Fiber Transceivers

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

SFP+ Cable Interconnect Assemblies Overview

SFP+ passive copper cable assemblies were developed specifically as a costeffective and lower-power alternative to optical fiber cables for short reach links in high-speed interconnect applications such as high performance computing (HPC), data center networking and network storage markets. The assemblies support data transfer rates up to 10 Gb/s per lane, meeting or exceeding current Industry Standard Specifications. These SFP+ fully-shielded assemblies combine twin-axial shielded cable with robust die cast connector interfaces for enhanced support of high frequency data rates.
SFP+ passive copper cable assemblies use twin-axial (twinax) shielded cable, which means that the signals travel over parallel pairs of conductors that have foil shields over each pair with a drain wire interstitial to the conductors. The cable contains 2 pairs, one for transmit (Tx) and one for receive (Rx) and each shielded pair is surrounded by an overall shield.
Twinax cable has all of the noise cancelling characteristics of twisted-pair cable with the added benefits of homogeneous geometry, which means that the cable’s 100 ohm impedance is much better controlled resulting in less signal loss.
Cross-section of SFP+ cable
These assemblies are called passive copper cables because there isn’t any signal conditioning circuitry (e.g. crosstalk or echo cancellation) contained within the SFP+ connector. Sometimes these assemblies are referred to as DAC or SFP+ Direct Attached cables or Cu cables. Inside the SFP+ MSA footprint optical cables can be used that require optical tranceivers or Active Optical Cables (AOC) that contain the transceiver as part of the cable.
There are four wire gauges to support our SFP+ passive copper cable assemblies: 30, 28, 26 and 24 AWG. These gauge offerings are based on the attenuation limits within the governing standards; longer cables require larger gauge copper wire.
SFP+ connectors contain EEPROMs within the connector’s diecast metal backshell. An EEPROM is an “Electrically Erasable Programmable Read-Only Memory” chip that is programmed at the factory with specific information about the cable assembly. This information is used by the network equipment that the cable is plugged into to get information that is used for signal transmission as well as information about the cable assembly such as vendor, serial number, part number, etc.
Applications and Compatibility
The initial interface option for 10 Gigabit Ethernet (10GbE) switches and servers were SFP+ ports because the 10GBASE-T standard and products were still being developed. As a result, there are many existing 10GbE switches and servers on the market that support SFP+ cabling. The SFP+ ports allow SFP+ direct attach (DAC) passive copper cable assemblies or SFP+ optical fiber modules to be used within the same port. The choices between SFP+ passive copper or active optical fiber are based on reach or the distance between the ports that are being connected as well as user preference. The passive SFP+ cable has a maximum reach of 5 meters which allows for Top of Rack (ToR) configurations and may also support Middle of Row (MoR) deployments as explained below.
The SFP+ DAC performance advantages over 10GBASE-T include lower latency and slightly lower power.
SFP+ interfaces take approximately the same space on a switch front panel as the RJ45 connector and, with SFP+ interfaces, switches can be built with 32 or 48 ports of 10 GbE in a single rack-unit height.
Cisco passive Twinax 5m
Some equipment vendors discourage the use of 3rd party cable assemblies by issuing a warning message if a non-vendor approved cable is plugged into a port. Most vendors, however, will provide a “work around”. Some errors are simple to clear just by acknowledging brand messaging. Fiberstore’s SFP+ direct attached passive copper cables have been tested by the University of New Hampshire’s Interoperability Lab (UNH IOL) and passed their 10Gigabit Ethernet interoperability testing with several vendors’ devices including: Cisco, Dell, Arista and Brocade.

What Is Main Difference Between Single Mode SFP and Multi Mode SFP?

SFP transceivers are commonly used and necessary in our daily life. And there are two kinds: single mode SFP and multi-mode SFP. However, maybe most people don’t know these two SFP transceivers are different. The following are the differences between single mode SFP and multi-mode SFP.
Diameter of the Core
Single mode SFP has a small diametral core that allows only one mode of light to propagate. Because of this, the number of light reflections created as the light passes through the core decreases, lowering attenuation and making the signal travel faster.
Compared with single mode SFP, multi-mode SFP has a larger diametral core that allows multiple modes of light to propagate. Thus when the light passes through the core, the number of light reflections increases, more data could pass through in a given time.
Transmission Distance
Single mode SFP are affected by waveguide dispersion caused by the light going down the fiber being wider than the core of the fiber. This allows more control of the path of the photons, but gets more influences from micro bends, twists, and stress on the fiber. So it’s often applied in long distance, higher bandwidth runs by Telcos, CATV companies, and Colleges and Universities.
Whereas multi-mode SFP are affected by Modal Dispersion, caused because the light rays follow different paths through the fiber and arrive at different times on the other end. Due to the high dispersion and attenuation rate with this type of fiber, the signal will become worse during its transmission over long distances. So multi-mode SFP could be typically used for short distance, data and audio/video applications in LANs. RF broadband signals, such as what cable companies commonly use, cannot be transmitted over multi-mode fiber.
Cost
Single mode SFP costs more than multi-mode SFP. Why does this happen? Because single mode SFP and multi-mode SFP use a different type of light emitting unit. Single mode SFP have fine laser i.e 1310nm or 1550nm. But multi-mode SFP having LED or lower wavelength type light emitting unit. Multi-mode couplers & lasers are a lot cheaper to manufacturer. Single-mode couplers & lasers are tuned & built to a much higher standard and cost a lot more to produce. So single mode SFP is always more expensive than multi-mode SFP.
The main purpose of showing these differences is for you to know SFP transceivers better and choose a suitable one. And the two transceivers are identified by colors on the outer jacket. The single mode SFP is yellow or blue, while the multi-mode SFP is orange or aqua.

An Irresistible Trend- 100 Gigabit Ethernet

In 2006, the IEEE 802.3 working group formed the Higher Speed Study Group (HSSG) and found that the Ethernet ecosystem needed something faster than 10 Gigabit Ethernet. Because the growth in bandwidth for network aggregation applications overpasses the capacities of networks employing link aggregation with 10 Gigabit Ethernet. HSSG is the first to propose that 100 gigabit per second for network aggregation applications. In January 2008, 100 Gb/s Task Force were formed. In June 2010, the 100GbE standards were approved. 100 Gigabit Ethernet (100GbE) means the computer networks transmitting data at rates of 100 gigabits per second.
There are two main advantages of 100 Gigabit Ethernet. And they are as following:
Fast speed: Compared with current 10 GbE protocol, 100 Gigabit Ethernet protocol is faster. The technology adheres to the principal Ethernet protocols and interfaces, while significantly boosting speeds and reducing network latency in the process. So for large users, 100 Gigabit Ethernet with heavy bandwidth and low latency is the best choice.
Low cost: Carriers and enterprises have to use multiple 10 Gbps connections to satisfy their aggregated bandwidth requirements because there are no alternatives to 10 Gbps. Each new 10 Gbps bandwidth step comes with additional switch and/or computer interfaces which are expensive. For example, the costs for 10x10G fiber cabling are more than the 1x100G cost. In one word, multiple 10 Gigabit Ethernet channels cost more than 100 Gigabit Ethernet network with just one channel.
As 100 Gigabit Ethernet comes into our daily life, 100G transceivers have been specifically designed to meet the needs of high speed. What kind of transceivers is suitable? CFP (C form-factor pluggable) transceiver supports the ultra-high bandwidth requirements of data communications and telecommunication networks that form the backbone of the internet. It’s compatible to 100 Gigabit Ethernet. Now there are CFP optical transceiver, CFP2 optical transceiver and CFP4 optical transceiver. From the diagram, the transceivers are smaller and smaller but with more optimization.
Today people are moving to the cloud in order to keep information in case it will be lost from one’s local memory storage on a computing device. Thus it increases the bandwidth demand. Most IT leaders believe that this causes significant network overload. Though 10 Gigabit Ethernet and 40 Gigabit Ethernet are common now, it’s said that 100 Gigabit Ethernet will make up over 50% of data center optical transceiver transmission capacity by 2019. So 100 Gigabit Ethernet is considered to be an irresistible trend to multiplex and transmit high amounts of data.

Copper SFP Transceiver for 1000BASE Applications

In the past, because of low cost and compatibility with existing LANs, 100Mb/s Ethernet was very popular. As people’s increasing demands for faster delivery of information, high bandwidth Ethernet LAN is evolving. 1000BASE (1 Gbps Gigabit Ethernet) came around and brought Ethernet technology to a new stage. Gigabit Ethernet, as the new networking techology was a viable solution for increased bandwidth requirements. Early implementation of the technology will be in high-speed backbones and specialized workgroups. The initial standards of 1000BASE were created and maintained by the 802.3z working group of the IEEE LAN-MAN Standards Committee in June 1998.
Now that 1000Mb/s Ethernet has been applied generally, the corresponding equipment like the cable and transceiver are needed to make the network the most effective.
Before 2000, SFP optical transceiver module combines transmit and receive functions in a compact, low power, low cost package format. Now it’s widely applied in Fibre Channel, Gigabit Ethernet (GbE), and SONET/SDH and supports data rates between 125 Mb/s and 4 Gb/s. Later some manufacturers make SFP ports with copper transceivers. The copper small form factor pluggable (SFP) transceiver can maintain both configuration flexibility and high port utilization with low cost for optical networks. Due to these advantages, the need for copper SFP transceivers increases obviously.
Configuration Flexibility with High Port-level
When there is no copper transceiver, users who want to support Ethernet traffic over both copper and fiber should offer two different line cards dedicated to one media or the other or, alternatively, hybrid cards with a fixed number of copper ports and optical cages. But this way is not very efficient because the available ports for each type of media rarely matched the network’s constantly evolving topologies.
In today’s network environments, systems must deal with the ongoing convergence of data, voice, and video traffic as well as topologies that mix Internet Protocol (IP) with legacy PDH traffic and integrate specialized requirements such as Fibre Channel or ATM. As GbE switches, routers, and multi-service provisioning platforms (MSPPs), for example, must provide port-level flexibility for handling both fiber and copper interfaces, thus copper SFP transceiver becomes the best way to optimize port-level flexibility.
A Cisco copper SFP and an optical SFP provide exactly the same physical and electrical interface for any port on the line card. This just needs a single line card design that can handle the entire spectrum of copper and fiber connections. The port utilization copper SFP transceiver can more efficiently to accommodate the changing network requirements.
Low Cost
The traditional dedicated line card approach increases inventory costs because it has low level of field reconfiguration. Copper SFP transceiver and a common line card design for all ports clearly reduce the inventory costs as well as complete the copper to fiber reconfiguration.
All in all, copper SFP transceiver has the advantages such as increased port density, improved system utilization, and low overall costs. Copper SFP transceiver offers users a level of flexibility that did not exist before. So Copper SFP transceiver will still gain its popularity.

Why Is CWDM so Popular?

WDM (wavelength division multiplexing) technology transmitting multiple signals on a single optical fiber by using different wavelengths to carry each signal has been used since 1980s. In the middle of 1990s, dense wavelength division multiplexing (DWDM) enabled carriers to extend the capacity of the SONET/SDH rings in the network core, without installing new fiber. As the development of data service, MAN has become a hot topic of network construction. However, DWDM system brings telecom operators very high costs in MAN construction. So the other kind of WDM technology, CWDM (coarse wavelength division multiplexing) emerged.
CWDM has fewer channels than DWDM. The energy from the lasers in a CWDM system is spread out over a larger range of wavelengths than is the energy from the lasers in a DWDM system. CWDM has many advantages like low cost, low power consumption and small volume. As an economical and practical short-distance WDM transmission system, CWDM becomes more and more recognized by people in many MAN applications just as follows.
Fiber Exhaust Relief
Fiber exhaust which means lack of network capacity occurs in metropolitan networks. CWDM is a simple and cost-effective way for people to solve fiber exhaust. By using CDWM, new services can be added over an existing single optical fiber. So to increase optical network capacity, people don’t need to replace existing equipment with higher bit rate transmission rate and install new fibers. Otherwise, it will cost too much because installing new fiber is a costly venture in metropolitan areas.
Low-cost WDM Deployments
CWDM system with reduced channels is beneficial for carriers in the metro-regional areas. It supports 4-channel configuration. Systems with 4 channels can quadruple the available capacity over an existing network segment, while offering a lower firstin deployment cost than an 8-channel system. For carriers, they should pay attention to two important points including cost and scalability when they need to upgrade to 8 channels systems. So CWDM is a good choice.
Central Office to Customer Premise Interconnection
CWDM is a good fit for metro-access applications such as Fiber to the Building (FTTB). An 8-channel CWDM network can deliver 8 independent wavelength services from the Central Office to multiple business offices located in the same building.
Due to the low cost, simplicity and scalability features of the latest products such as CWDM modules, CWDM systems is a good choice for overbuilding with Next Generation SONET, DWDM, and proprietary solutions. CWDM is becoming more and more popular among carriers who need to upgrade their networks to accommodate current of future needs while minimizing the use of valuable fiber strands especially in the metropolitan areas.

General Understanding of LC to LC Fiber Optic Cables

Fiber optic patch cords are also known as fiber optic jumpers or fiber optic patch cables. Fiber optic patch cords are designed to provide optical connection for fiber networks within structured cabling systems. It’s a quick and easy method for routing fiber patches in data centers, head-ends, cellular hubs and central offices. It’s composed of two parts: optical connector and fiber optic cable. As to the connector, fiber patch cords could be terminated with LC/SC/ST/FC/MTRJ/MU/SMA connectors on both ends.
With the increasing deployment of fiber in the LAN, the need for small form factor fiber optic connectors is becoming urgent. The main reasons are deployment cost and space savings for cabling hardware and equipment interfaces. LC connector is a small form factor connector with half size of SC connector. The connector was invented by Lucent Technologies. Lucent is an American multinational telecommunications equipment company. So LC stands for Lucent Connectors. The connectors are made to support Telecom and Datacom networks.
The LC fiber patch cable is with a small form factor connector and suitable for high density applications. It’s compliant with IEC, Telcordia, EIA/TIA. One of the fiber optic patch cords LC series is LC to LC fiber patch cord. LC to LC fiber patch cord includes LC-LC single-mode and LC-LC multi-mode types.
LC-LC single-mode has two versions like simplex and duplex. Single-mode simplex fiber cable is single strand and single-mode duplex fiber cable is zipcord cable which is tight-buffered and jacketed. To be easily identified, the color of the cable jacket is often yellow. And the diameter is usually 1.8mm, 2mm or 3mm. The LC-LC single-mode fiber optic cables have the features of good performance and fast delivery. It’s used for long distance transmission.
LC-LC multi-mode patch cords are composed of a polymer outer body and inner assembly fitted with a precision alignment mechanism. As single-mode patch cords, this kind has both simplex and duplex versions too. These cables are with typical 50/125 and 62.5/125 optional multi-mode fiber. The cable diameter is 0.9mm, 2mm or 3mm. Due to the thick core size, the signal degradation caused by the refraction occurs. Thus it’s usually used for short distance signal transmission.
LC to LC fiber optic cables, as one kind of fiber optic patch cords, have many advantages such as high return loss, low insertion loss and back reflection loss, good durability, high temperature stability, good interchangeability and duplication. Thus they are widely used in Gigabit Ethernet and fiber channel, multimedia, telecommunication, and high speed data transmission throughout the network, etc.