Author: Fiber-MART.COM

In recent years, 40 Gigabit Ethernet (GbE) has gained more popularity and the market of 40GbE is encouraging. But with the rapid growth of the new standard 100GbE, a new voice is announcing, namely 25GbE. As the increasing bandwidth requirements of private and public cloud data centers and communication service providers, 25GbE will to have a significant impact on server interconnect interfaces. Now you have two upgrade paths to 100G, 10G-25G-100G and 10G-40G-100G. Which one to choose? This post will make a comparison of 25GbE and 40GbE cabling, hoping it can help you make an appropriate decision.

25GbE Cabling Overview

25GbE is a standard developed by developed by IEEE 802.3 task forces P802.3by, used for Ethernet servers and switches connectivity in a datacenter environment. The single-lane design of 25 GbE gives it a low cost per bit, which enables cloud providers and large-scale data center operators to deploy fewer switches to meet the needs while still scaling their network infrastructure.

25GbE physical interface specification supports two main form factors, SFP28 (1×25 Gbps) and QSFP28 (4×25 Gbps). 25GBASE-SR SFP28 is an 850nm VCSEL 25GbE transceiver available in the market. It is designed to transmit and receive optical data over 50/125µm multi-mode optical fiber (MMF) and support up to 70m on OM3 MMF and 100m on OM4 MMF (LC duplex). In fact, using an SFP28 direct attach copper (DAC) cable for switches direct connection is a preferred option now. In addition, a more cost-effective solution is to use a QSFP28 to 4xSFP28 breakout cable to connect a 100GbE QSFP28 switch port with four SFP28 ports. DAC cable lengths are limited to three meters for 25GbE. Thus, active optic cable (AOC) solutions are also used for longer lengths of applications.

40GbE Cabling Overview

40GbE is a standard developed by the IEEE 802.3ba task force. The official development of 40GbE standards first began in January 2008, and were officially approved in June 2010. At the heart of the 40GbE network layer is a pair of transceivers connected by a fiber optic cable, OM4 or OM3 fiber cable. Fiber optic transceivers are plugged into either network servers or a variety of components, including interface cards and switches.

There are several standard form factors of 40GbE transceivers in the whole evolution. The CFP (C form-factor pluggable) transceiver uses 12 Tx and 12 Rx 10Gbps lanes to support one 100GbE port, or up to three 40GbE ports. With its large size, it can meet the needs of single-mode optics and can easily serve multi-mode optics or copper. But it is gradually falling behind since the increasing demand for high density. Another form factor is the CXP. It also provides twelve 10Gbps lanes in each direction, but is much smaller than the CFP and serves the needs of multi-mode optics and copper. At present, the most commonly used 40GbE form factor is the QSFP+ (quad small form-factor pluggable plus). It has the similar size with CXP but can provide four Tx and four Rx lanes to support 40GbE applications for single-mode, multi-mode fiber and copper.

Fiber optic cabling and copper cabling are both available for 40 GbE. The supportable channel length depends on the cable and the transceiver type. For data center 40GbE fiber optic cabling, OM3 and OM4 multi-mode cables are generally recommended because they can support a wider range of deployment configurations compared to copper solutions, and lower costs compared to single-mode solutions. MPO/MTP connectors are used at the multimode transceivers to support the multifiber parallel optics channels. For copper solutions, you can use QSFP+ direct attach copper cables, such as Cisco QSFP+ breakout cable. There are a lot of options, both active and passive, like Cisco QSFP-4SFP10G-CU5M compatible 40G QSFP+ to 4x10G SFP+ passive direct attach copper breakout cable (as shown below).

25GbE Cabling vs 40GbE Cabling

Compared to 40 GbE, 25GbE seems to be more suitable and cost-effective for cloud and web-scale data center applications. Using 25GbE with QSFP28 transceivers, users can deliver a single-lane connection, similar to the existing 10GbE technology but with 2.5X faster performance. In addition, 25GbE can provide superior switch port density by requiring just one lane (vs. 4 lanes with 40 GbE). Thus, it costs less and requires lower power consumption. Benefits of 25GbE compared to 40GbE are shown as below:

Greater port density vs 40 GbE (one lane vs. four lanes)

Maximum switch I/O performance and fabric capability

Lower cost versus 40 GbE

Reduced capital expenditures (CAPEX) and operational expenditures (OPEX)

Fewer ToR switches and fewer cables

Requires less power, cooling, and footprint

Leverage of the existing IEEE 100GbE standard

Summary

25GbE seems to be a preferred option in the next step. It can provide up to 2.5 times faster performance than the existing 10GbE connections while maximizing the Ethernet controller bandwidth/pin and switch fabric capability. It can also provide greater port density with lower cost compared to 40GbE solutions. The trend will always be wider band and higher speed and port density. 25GbE or 40 GbE, let’s wait and see how things play out.

Over the years of SFP transceiver communication existence, there have been numerous different standards introduced. The great thing about SFP transceivers in networking hardware is that they allow a single piece of equipment, such as a switch, to support different wiring and transmission formats. The problem comes when trying to figure out which of the many transceiver types out there you need. There are several different types of SFP transceivers capable of supporting a multitude of communication standards, such as: CWDM/DWDM, SONET, Fibre Channel, Fast Ethernet and Gigabit Ethernet.

CWDM/DWDM SFP Transceivers

WDM, or wavelength-division multiplexing, is a type of technology that allows a transceiver to have different wavelengths assigned to it.Coarse wavelength-division multiplexing (CWDM) SFP transceivers are capable of transmitting data at eight different wavelengths ranging from 1470nm to 1610nm. CDWM SFP transceivers are color coded, to help identify which wavelength is mapped to the transceiver.Dense wavelength-division multiplexing (DWDM) SFP transceivers are available in 32 different wavelengths, and offer high-capacity bandwidth for serial optical data communications. DWDM SFP transceivers are slightly more expensive than CWDM SFP transceivers, but the more densely spaced channels allow for a greater number of wavelengths to travel over a single fiber.Both CWDM and DWDM SFP transceivers can be used to transmit data over Gigabit Ethernet, SONET and Fibre Channel.

SONET SFP Transceivers

Synchronous optical networking (SONET) technology enables the transmission of a large volume of data over long distances. SONET can be used to transmit multiple streams of data simultaneously over fiber optic mediums using laser beams and LEDs.SFP transceivers are built to transmit data over SONET at varying rates (OC-3, OC-12 and OC-48) and with different reaches (short-reach, intermediate-reach, and long-reach). SONET SFP transceivers are able to transmit data over both singlemode and multimode fiber.

Fibre Channel SFP Transceivers

Fibre Channel is a protocol which is used primarily in “Storage Area Networks”. It comes in different speeds like 1xFC, 2xFC, 4xFC, 8xFC and 16xFC. Fibre Channel was developed as a lossless protocol in a time when switches were less reliable than they are today. When using Ethernet as a protocol, frames were dropped, which created a problem for applications like data traffic. With the advent of greater technology, switches are now much more reliable; however, Fibre Channel still holds a small advantage over Ethernet when it comes to consistency and latency.Fibre Channel SFP transceivers are modules commonly used in storage area networks (SAN) and are available in 1, 2, 4, 8, 10, 16 and 20Gbps data transmission rates. Fibre Channel SFP transceivers can be used in both singlemode and multimode fiber applications.

Fast Ethernet and Gigabit Ethernet

Fast Ethernet is slowly being replaced with Gigabit Ethernet. Fast Ethernet SFP transceivers were originally designed to transmit data at 10Mbps, and eventually reached transmission speeds of 100Mbps (100Base). 100Base rate Fast Ethernet transceivers are available in the following interface types: FX, SX, BX and LX10.With the development of Gigabit Ethernet, SFP transceiver transmission rates increased to 1000Mbps (1000Base). 1000Base rate Gigabit Ethernet SFP transceivers are available in the following interface types: T, SX, LX, LX10, BX10, and the non-standard EX and ZX.

fiber-mart.COM is sure to have the right SFP transceiver for your network! We carry a full line of both name-brand and affordable 100% compatible transceivers of every type your business could possibly need. Contact us today for a free consultation on which standards meet your business needs, or to discuss fiber connectivity network solutions that will best support your future business plans.

As a result of data center consolidation, server virtualization, and new applications that require higher data transport rates, 10Gbps infrastructure is becoming overwhelmed by today’s data center requirements, making the shift to 40 and 100 Gbps inevitable, especially in the network aggregation layer and core. How to upgrade the cabling infrastructure and migrate to the 40Gbps era in a cost-effective way? Cisco 40G QSFP (quad small form-factor pluggable) bidirectional (BiDi) technology provides a feasible and effective method, which will be introduced in the following text.

What Is 40G QSFP BiDi Transceiver?

c The Cisco BiDi transceiver supports link lengths of 100m and 150m on laser-optimized OM3 and OM4 multimode fibers. It complies with the QSFP MSA specification, enabling customers to use it on all QSFP 40 Gbps platforms to achieve high-density 40 Gigabit Ethernet networks.

How Does 40G QSFP BiDi Transceiver Work?

Cisco QSFP BiDi transceiver technology converts four channels each of 10Gbps transmit and receive signals to two bidirectional channels of 20Gbps signals, which means that the Cisco QSFP BiDi transceiver has two 20Gbps channels, each transmitted and received simultaneously over two wavelengths on a single MMF strand. The technology uses specialized, multilayer, thin-film dielectric coating and lensing, which allows components to both pass and reflect optical signals at the same time. And it uses Bidirectional Optical Sub-Assembly (BOSA) technology to support two wavelengths (20 Gbps total) on each fiber. The connection can reach 100 meters on OM3 MMF or 150 meters on OM4 MMF, which is the same as 40Gbps SR4. Picture below shows the technology concept of the Cisco QSFP BiDi transceiver.

Why Choose 40Gbps QSFP BiDi Transceiver?

The Cisco QSFP BiDi transceiver transmits full-duplex 40Gbps traffic over one dual-fiber LC connector OM3 or OM4 MMF cable. It provides the capability to reuse 10Gbps fiber infrastructure. In other words, it enables data center operators to upgrade to 40Gbps connectivity without making great changes to the previous 10Gbps fiber cable plant. By using the existing 10 Gigabit Ethernet duplex multi-mode fiber (MMF) infrastructure for 40 Gigabit Ethernet, the Cisco BiDi transceiver offers significant cost savings and simplifies data center upgrading. It allows for zero-cost fiber migration by reusing the current 10Gbps cabling for 40Gbps device connectivity. 40Gbps QSFP BiDi transceiver reduces overall costs and installation time for customers migrating data center aggregation links to 40Gbps connections. Using Cisco BiDi transceivers offers 75% less fiber and MPO requirements, reduced cable sprawl and rack footprints, and investment protection with future support for 100 Gbps over duplex fiber.

Conclusion

Cisco 40G QSFP BiDi technology removes 40Gbps cabling cost barriers for migration from 10Gbps to 40Gbps connectivity in data center networks. It is quite a competitive option among all those various choices for 40 Gigabit Ethernet applications, such as QSFP+ transceiver, QSFP+ breakout cable or active optical cable. Compared with them, Cisco 40G QSFP BiDi transceivers provide simpler and less expensive 40Gbps connectivity compared to other 40Gbps transceiver solutions. Anyway, you choose the most appropriate one for your applications.

In communication networks, many transmission lines need bidirectional transmission. This need leads to the development of Bidirectional (BiDi) transceivers, which can transmit and receive data to/from interconnected equipment through a single optical fiber. BiDi transceivers are fitted with wavelength division multiplexing (WDM) diplexers, which combine and separate data transmitted over a single fiber based on the wavelengths of the light. BiDi transceivers must be deployed in matched pairs, with their diplexers tuned to match the expected wavelength of the transmitter and receiver that they will be transmitting data from or to. In this post, a kind of BiDi transceiver, 1000BASE-BX SFP BiDi transceiver will be introduced.

Introduction

1000BASE-BX is a part of the Gigabit Ethernet standard related to transmission over fiber optic cable. 1000BASE-BX SFP modules are compliant with SFP Multi-Source Agreement (MSA) specification and SFF-8472, and conform to the IEEE 802.3ah 1000BASE-BX10 standard. 1000BASE-BX SFP modules include 1000BASE-BX-U SFP module and 1000BASE-BX-D SFP module. These two SFP modules must be used in pairs to permit a bidirectional Gigabit Ethernet connection using a single strand of single mode fiber (SMF) cable. These transceivers transmit and receive signals on one fiber strand using two wavelengths in each direction. These hot pluggable optical transceivers consist of two sections: the transmitter section uses 1490nm DFB laser/1310nm Fabry-Perot laser, and the receiver section uses 1310nm/1490nm receiver accordingly. The 1000BASE-BX-D SFP operates at wavelengths of 1490nm TX/1310nm RX, and the 1000BASE-BX-U SFP operates at wavelengths of 1310nm TX/1490nm RX. These transceivers use standard simplex LC connectors for fiber cable connection and provide a long transmission distance of up to 10 km.

Key Features

Data rate up to 1.25 Gbps

Hot-pluggable SFP footprint

1490 nm DFB Transmitter and 1310 nm PIN Receiver

1310 nm FP Transmitter and 1490 nm PIN Receiver

Transmission distance up to 10 km

Simplex LC connector

Low power dissipation

Digital diagnostic monitor interface is compliant with SFF-8472

Compliant with SFP MSA Specification

Compliant with IEEE 802.3z Gigabit Standard

RoHS compliance

1000BASE-BX-D SFP

1000BASE-BX-D SFP supports link length of up to 10km point to point on single mode fiber (1490nm-TX/1310nm-RX wavelength) at 1Gbps bidirectional. This optic uses an LC connector. The picture below show a Cisco GLC-BX-D compatible 1000BASE-BX-D SFP 1490nm-TX/1310nm-RX transceiver. The GLC-BX-D is a small form factor pluggable module for Gigabit Ethernet 1000BASE-BX and Fiber Channel communications. The GLC-BX-D transceiver operates at 1490Tx/1310Rx wavelength. It is compatible with the IEEE 802.3ah 1000BASE-BX10-D standards. A 1000BASE-BX-D device is always connected to a 1000BASE-BX-U device with a single strand of standard SMF.

1000BASE-BX-U SFP

1000BASE-BX-U SFP supports link length of up to 10km point to point on single mode fiber (1310nm-TX/1490nm-RX wavelength) at 1Gbps bidirectional. This optic uses an LC connector. The communication over a single strand of fiber is achieved by separating the transmission wavelength of the two devices. 1000BASE-BX-D transmits a 1490nm channel and receives a 1310nm signal, whereas 1000BASE-BX-U transmits at a 1310nm wavelength and receives a 1490nm signal. A wavelength-division multiplexing (WDM) splitter integrated into the SFP to split the 1310nm and 1490nm light paths. The GLC-BX-D and GLC-BX-U SFPs also support digital optical monitoring (DOM) functions according to the industry-standard SFF-8472 multisource agreement (MSA). This feature gives the end user the ability to monitor real-time parameters of the SFP, such as optical output power, optical input power, temperature and transceiver supply voltage. The picture below show a Cisco GLC-BX-U compatible 1000BASE-BX-U SFP 1310nm-TX/1490nm-RX transceiver.

Applications

Gigabit Ethernet

Fiber Channel Links

Switch to switch interface

Switched backplane applications

Pouter/Server Interface

Other optical transmission systems

Conclusion

New organizational applications, virtualization, and data center consolidation trends are pushing your server I/O requirements to meet higher needs than before. With new BiDi optical technology, SFP BiDi transceivers make it much easier for you to upgrade your networks.

As we know, fiber optic patch cords are capped at both ends with fiber optic connectors to allow them to be rapidly and conveniently connected to telecommunication equipment. Fiber optic connector is one of those high quality ceramic components used to achieve accurate and precise connections of the fiber ends. It is a simple device which allows fiber links to be readily connected and disconnected.

How to install fiber optic connectors to optical fibers so that they can achieve accurate and precise connections? The method for attaching fiber optic connectors to optical fibers varies based on connector types. Installation ways of fiber optic connectors largely depends on the connector types. Generally, connectors can be categorized into no-epoxy/no-polish connectors and epoxy-and-polish connectors. The following text elaborates on how to install these two kinds of connectors respectively.

No-epoxy/no-polish Connector Installation

How to install no-epoxy/no-polish (NENP) connectors to optical fibers? A no-epoxy/no-polish connector includes an precisely polished endface. When installing an NENP connector, there is no need to use an epoxy or to polish the endface. The field fiber is mechanically spliced to a factory-cleaved fiber stub. The following picture is an illustration of  no-epoxy/no-polish connector installation.

The installation process begins with preparing the field fiber, which is done by stripping the protective coating down to the bare glass. Once the fiber is cleaned, it is then cleaved with a precision cleaver. Next step is to insert the field fiber into the connector until it is seated against the factory-stubbed fiber and locked into place mechanically by a rotating cam or other means. Typically this step is achieved by using a tool that holds the connector and activates the mechanical splice by a button or lever.

Epoxy-and-polish Connector Installation

How to install epoxy-and-polish (EP) connectors to optical fibers? The most common types of EP connectors use heat- or anaerobic-curing techniques. A heat-cure connector uses heat to harden an epoxy, which takes several minutes. An anaerobic EP connector uses a two-part epoxy, a hardener that is inserted into the connector and an activator on the fiber.

To install an EP connector, an epoxy must be inserted into the connector ferrule first to form a bond between the field fiber and the connector’s ferrule, and then the endface needs to be hand-polished. Next, the field fiber is stripped down to the bare glass and cleaned. If the connector is heat-cure, the fiber is inserted into the connector and placed in an oven for the epoxy to cure. If the type of connector is anaerobic, the bare fiber is painted with an activator and inserted into the connector. Once the epoxy has been cured, the fiber stub which is protruding above the ferrule is scribed and removed. The final step is to polish the endface of the connector using a fixture and several different polishing films.

Notes for Fiber Optic Connector Installation

Besides different installation methods for different connector types, several things need to be paid attention to when installing fiber optic connectors, especially when a fiber patch cord has two different types of connectors, such as LC-SC fiber optic patch cord or FC-ST fiber optic patch cord.

• The bared fiber must be thoroughly cleaned with fiber optic cleaning fluid. Never clean the fiber with a dry tissue. Before the connection is made, the end of each fiber must have a smooth finish that is free of defects such as hackles, lips, and fractures.

• The cable should be cut about one inch longer than the required finished length.

• Be sure to use strippers made specifically for use with fiber rather than metal wire strippers because damage can occur and then weaken the fiber.

Any problems with a connector, such as poor installation and uncleanness, can greatly influence the transmission and reception of the light power. And such problems may render the fiber optic system inoperative. So it is very necessary to know something about installation of fiber optic connectors

Fiber Optic Connector Selection

Connector is an integral component of the cabling system infrastructure, which keeps the information flowing from cable to cable or cable to device. There are various connector types, including LC, FC, ST, SC, MTRJ, MPO, MTP, DIN, E2000, MU, etc. To design a fiber optic system, optical connector selection is also a very important decision. When selecting an optical connector, you have to take fiber types, polishing styles and number of fibers all into consideration.

Polishing Styles: There are mainly three kinds of polishing styles, PC (physical contact), APC (angled physical contact), and UPC (ultra physical contact). PC, UPC and APC refer to how the ferrule of the fiber optic connectors is polished. PC connector is used in many applications. UPC connectors are often used in digital, CATV, and telephony systems. APC connectors are preferred for CATV and analog systems. The picture below shows these three kinds of polishing styles.

Fiber Types: Single-mode and multi-mode optical fiber are two commonly used fiber types. Accordingly, there are single-mode optical connector and multi-mode optical connector. ST and MTRJ are the popular connectors for multi-mode networks. LC connector and SC connector are widely used in single-mode systems. Single-mode fiber optic connectors can be with PC, or UPC or APC polish, while multi-mode fiber optic connectors only with PC or UPC polish.

Number of Fibers: Simplex connector means only one fiber is terminated in the connector. Simplex connectors include FC, ST, SC, LC, MU and SMA. Duplex connector means two fibers are terminated in the connector. Duplex connectors include SC, LC, MU and MTRJ. Multiple fiber connector means more than two fibers (for up to 24 fiber) are terminated in the connector. These are usually ribbon fibers with fiber count of 4, 6, 8, 12 and 24. The most popular ribbon fiber connector is MT connector.

Conclusion

The key to designing a successful fiber optic system is understanding the performance and applications of different kinds of fibers, cable constructions and optical connectors, and then utilizing the appropriate components. fiber-mart.com provides a wide range of fiber optic cables and connectors. Fiber optic cables can be available in single-mode, multimode, or polarization maintaining, and they can meet the strength and flexibility required for today’s fiber interconnect applications.