G.fast Offers Fiber Speed Ethernet Over Copper

The demand for higher data rates is continuously increasing driven by the applications like Cloud Computing, Big Data and Internet of Things. Meanwhile, the strong market competition makes the network operators to improve the network architecture and deliver high speed services. Pure fiber network should be the best solution. There is no wonder that the fiber network is the trend of the future and it is gradually extended closer to users during the transition from copper-based access networks to pure fiber networks. However, it is not favorable to connect the fiber directly to the customer premises and the cost is high in some cases, like old buildings. To find the fast and cost-effective way to deliver Gigabit speed Ethernet, copper access technology is being applied in some cases. This technology is known as G.fast.

G.fast and FTTdp

G.fast, based on the latest VDSL technology including cross talk cancellation and re-transmission, is designed for use in a 'last-mile' of less than 250 meters. Combining the advantages of fiber optic access technology and copper access technology, G.fast can deliver data at fiber speed to the customers using telephone copper wires.

The problem with G.Fast is that its ultra-fast speeds only work over very short distances. To shorten the copper distance, FTTdp is usually applied with G.fast. "dp" here stands for "distribution point". This solution brings the fiber optic cable out of street cabinets and moves it closer to home via the distribution point. The following network diagram shows the difference of FTTH and FTTdp using G.fast. The blue lines represent fiber optic cable, the red ones represent copper wire.

G.fast Shifts the Limits of Copper

It seems that there is no need for copper access in building a FTTx connection. But in practice, connecting the fiber directly to the customer premises causes some disadvantages which can be solved by G.fast.

There might be many difficulties when deploying fibers to the user homes, especially some existing buildings. Sometime it is even not possible to deploy fibers to the user homes. In addition, most in-house telephone installations still rely on copper cables for most existing and newly constructed buildings because fibers are expensive and difficult to handle. There is no need to deploy fiber optic cable in building and home when delivering Gigabit Ethernet with G.fast.

The fiber optic based customers premises equipment (CPE) are usually installed by technician. Compared with fiber optic connections, copper-based CPE installation is simple. Just connecting the CPE to the telephone plug with the delivered cable would finish the installation, which can be installed by customer. Thus, G.fast can save the cost for new users and makes the home installation much easier.

Optical fibers can be broken or have transmission loses when wrapped around curves and optical fibers require more protection around the cable compared to copper. What’s more, the fault location from the CPE is not easy. It would cost more to maintain the fiber connections compared with copper connections achieved by G.fast.

G.fast Paves the Way to FTTH

At first glance, G.fast is limiting the transmission from copper to fiber. Actually, G.fast accelerates the deployment of fiber optic networks. It cost a lot of time and money to process the paperwork and get permission of the subscriber before deploying the fiber optic cable. The processing is complicated. Hardware foundation is the main advantages of G.fast which eliminates the need to rewire the whole building and still allows a noteworthy uplift in access speeds. Copper is everywhere in telecommunication network. The hybrid copper/fiber approach—G.fast making full use of the telephone wires in the buildings actually makes the customers closer to optical fibers in time save and cost save manners. In this way, the transmission from copper to fiber is actually being promoted by G.fast.

Weighing time, broadband speed and cost, operators figure out that applying G.fast in FTTH is an economical and time-saving way to bring Gigabit speed Ethernet to the users. To capture market share of broadband service, some network operators are considering to use G.fast. Alcatel-Lucent and communications services company BT have already started a consumer trial of G.fast technology in Gosforth (situated in North-Eastern England), for offering ultra-broadband access to consumers.

Source: http://www.fiber-optic-tutorial.com/g-fast-offers-fiber-speed-ethernet-over-copper.html

Do You Know Digital Diagnostic Monitoring?

Cisco announced the end of sale of its SFP transceiver Cisco GLC-SX-MM transceiver and published a replacement—Cisco GLC-SX-MMD transceiver in 2012. The module numbers of the two transceiver only differ in one letter "D". This "D" mainly represents a function of Cisco GLC-SX-MMD transceiver and is inherited by most of optical transceivers offered today. It is the main reason why Cisco GLC-SX-MMD transceiver can replace its predecessor. What is this "D"? Why the GLC-SX-MMD can replace GLC-SX-MM? This article is to offer the answers to these questions.

What Is Digital Diagnostic Monitoring (DDM)?

"D" in GLC-SX-MMD represents the DDM function which is short for digital diagnostic monitoring according to the industry standard MSA (Multi-Source Agreement) SFF-8472 and is also known as DOM (Digital Optical Monitoring). When buy fiber optic transceiver today, you will have the option with or without DDM/DOM. And most of the modern transceivers are with the DDM function. This technology allows the user to monitor real-time parameters of the fiber optic transceivers, like optical input/output power, temperature, laser bias current, and transceiver supply voltage, etc.

What Can Digital Diagnostic Monitoring Do?

Literally, DDM function can provide component monitoring on transceiver applications in details. However, DDM’s application is not limited to this. The SFF-8472 added DDM interface and outlined that DDM interface is an extension of the serial ID interface defined in GBIC specification, as well as the SFP MSA. DDM interface includes a system of alarm and warning flags which alert the host system when particular operating parameters are outside of a factory set normal operating. Thus, DDM interface can also enable the end user with the capabilities of fault isolation and failure prediction. This part is to illustrate what can be done with DDM.

Component Monitoring: The DDM enables the end user to monitor key parameters in the performance of the fiber optic transceiver including the following:

• Transceiver temperature
• Transceiver supply voltage
• Laser bias current
• Transmit average optical power
• Received optical modulation amplitude (OMA) or Average Optical Power

The real-time diagnostic parameters can be monitored to alert the system when the transceiver’s specified operating limits are exceeded and compliance cannot be ensured.The following picture shows the eye diagram illustrating optical figures of merit.

Fault isolation: The DDM function can be used to isolate the particular location of fault in fiber optic network system. Combining the DDM interface status flags, transceiver hard pins and diagnostic parametric monitor data, the specific location and cause of a link failure can be pinpointed.

Failure prediction: The DDM can also be used to help in failure prediction on fiber optic links, which is based on the transceiver parametric performance. Although, this application is not yet fully mature, but there is still room for improvement. There are two basic types of failure conditions that can be seen on fiber optic transceivers:

• Device faults—A device non-operation or malfunction. Typically applied more to transmitter performance, due to nature of semiconductor lasers.
• High error rate conditions—Operating conditions are such that transceiver is operating at its signal-to-noise limit. Applies more to fiber optic receiver performance.

Providing parameter monitoring, fault isolation, and failure prediction, fiber optic transceivers with DDM help to ensure that the business can be proactive in preventative maintenance of the network and ensure business continuity. And it would easy to explain why modern transceivers are with DDM and why GLC-SX-MMD can replace GLC-SX-MM. It is irresistible development trend of industry and technology.

What should be mentioned is that although optical transceivers with DDM are much popular than those without DDM, some user still use the older optical transceivers in consideration of the upgrading costs. To satisfy the customers’ needs, optical transceivers with DDM and without DDM are provided by the vendors like Fiberstore.

Source: http://www.fiber-optic-tutorial.com/do-you-know-digital-diagnostic-monitoring.html