How Much Do You Know About OADM?

The OADM, short for optical add drop multiplexer, is one of the key components for dense wavelength division multiplexing (DWDM) and ultra wide wavelength division multiplexing (UW-WDM) optical networks. OADM technology is used to cost effectively access part of the bandwidth in the optical domain being passed through the in-line amplifiers with minimum amount of electronics.
An OADM can be considered as a specific type of optical cross-connect, widely used in wavelength division multiplexing (WDM) systems for multiplexing and routing fiber optic signals. They selectively add and drop individual or sets of wavelength channels from a dense wavelength division multiplexing (DWDM) multi-channel stream. OADMs are used to cost effectively access part of the bandwidth in the optical domain being passed through the in-line amplifiers with the minimum amount of electronics.
OADMs have passive and active modes depending on the wavelength. In passive OADM, the add and drop wavelengths are fixed beforehand while in dynamic mode, OADM can be set to any wavelength after installation. Passive OADM uses WDM filter, fiber gratings, and planar waveguides in networks with WDM systems. Dynamic OADM can select any wavelength by provisioning on demand without changing its physical configuration. It is also less expensive and more flexible than passive OADM. Dynamic OADM is separated into two generations.
A typical OADM consists of three stages: an optical demultiplexer, an optical multiplexer, and between them a method of reconfiguring the paths between the optical demultiplexer, the optical multiplexer and a set of ports for adding and dropping signals. The MUX multiplexes the wavelength channels that are to continue on from DEMUX ports with those from the add ports, onto a single output fiber, while the DEMUX separates wavelengths in an input fiber onto ports. The reconfiguration can be achieved by a fiber patch panel or by optical switches which direct the wavelengths to the MUX or to drop ports. All the light paths that directly pass an OADM are termed cut-through lightpaths, while those that are added or dropped at the OADM node are termed added/dropped lightpaths.
OADM works as follows: the WDM signals from line containing N wavelength channels enter the OADM “Main Input” side, depending on your business needs, from N wavelength channel, selectively from the road-side (Drop) required by the output wavelength channel, accordingly from the road-end (Add) enter the desired wavelength channel. Regardless of other local wavelength channel directly through the OADM, and routing wavelength channels multiplexed together, from the output terminals of the circuit of OADM (Main Output) output. The following picture shows the basic operation of an OADM.
Physically, there are several ways to realize an OADM. There are a variety of demultiplexer and multiplexer technologies including thin film filters, fiber Bragg gratings with optical circulators, free space grating devices and integrated planar arrayed waveguide gratings. The switching or reconfiguration functions range from the manual fiber patch panel to a variety of switching technologies including microelectromechanical systems (MEMS), liquid crystal and thermo-optic switches in planar waveguide circuits.
CWDM and DWDM OADM provide data access for intermediate network devices along a shared optical media network path. Regardless of the network topology, OADM access points allow design flexibility to communicate to locations along the fiber path. CWDM OADM provides the ability to add or drop a single wavelength or multi-wavelengths from a fully multiplexed optical signal. This permits intermediate locations between remote sites to access the common, point-to-point fiber message linking them. Wavelengths not dropped, pass-through the OADM and keep on in the direction of the remote site. Additional selected wavelengths can be added or dropped by successive OADMS as needed.
fiber-mart.COM provides a wide selection of specialized OADMs for WDM system. Custom WDM solutions are also available for applications beyond the current product designs including mixed combinations of CWDM and DWDM.

Do I Need a Gigabit Switch or 10/100Mbps Switch?

Ethernet network speeds have evolved significantly over time and typically range from Ethernet (802.11) at 10Mbps, Fast Ethernet (IEEE 802.3u) at 100Mbps, Gigabit Ethernet (IEEE 802.3-2008) at 1000Mbps and 10 Gigabit Ethernet (IEEE 802.3a) at 10Gbps. Meanwhile, Ethernet switches have also escalated from 10/100Mbps switch to Gigabit switch, 10GbE switch, and even 100GbE switches. The topic came up frequently that “Do I Need a Gigabit Switch or 10/100Mbps Switch?” Gigabit switch vs 10/100Mbps switch, which do I need to satisfy my network speeds requirement? This post will give you the answer.
Gigabit Switch: the Mainstream on Network Switch Market
Gigabit switch is an Ethernet switch that connects multiple devices, such as computers, servers, or game systems, to a Local Area Network (LAN). Small business and home offices often use Gigabit switches to allow more than one device to share a broadband Internet connection. A gigabit switch operates in the same manner, only at data rates much greater than standard or Fast Ethernet. People can use these switches to quickly transfer data between devices in a network, or to download from the Internet at maximum speeds of 1000Mbps. If a switch says “Gigabit”, it really means the same thing as 10/100/1000, because Gigabit switches support all three speed levels and will auto-switch to the appropriate one when something is plugged in. The following is a Gigabit 8 port poe switch with 8 x 10/100/1000Base-T RJ45 Ethernet ports.
10/100Mbps Switch: Still Alive and Well for Some Reason
10/100Mbps switch is a Fast Ethernet switch released earlier than Gigabit Ethernet switch. The data speed of 10/100Mbps switch is rated for 10 or 100Mbps. When a network switch says “10/100”, it means that each port on the switch can support both 10Mbps and 100Mbps connection speeds, and will usually auto-switch depending on what’s plugged into it. Currently, few devices run at 10Mbps, but it is still alive on the market for some reason. Actually, 10/100 is sufficient for internet browsing and Netflix. But if you will be doing more than one thing with your network connection, such as file transfers, or the set-top box, I would recommend you go with the Gigabit switch.
Gigabit Switch vs 10/100Mbps Switch: How to Choose?
Network engineers who refresh the edge of their campus LAN encounter a fundamental choice: Stick with 100Mbps Fast Ethernet or upgrade to Gigabit Ethernet (GbE). Vendors will undoubtedly push network engineers toward pricier GbE, but network engineers need to decide for themselves which infrastructure is right for the business. Currently, Gigabit switch is much more popular than Fast Ethernet 10/100Mbps switch. Because gigabit switch used in tandem with a gigabit router will allow you to use your local network at speeds up to ten times greater than 10/100Mbps switch. If either of these component are not gigabit, the entire network will be limited to 10/100 speeds. So, in order to use the maximum amount of speed your network can pump out, you need every single component in your network (including you computers) to be gigabit compliant. In addition, by delivering more bandwidth and more robust management, Gigabit switches are also more energy efficient than 10/100Mbps switches. This offers enterprises the opportunity to lower their power consumption on the network edge.
There’s a multitude of switch options to choose from on the dazzling market. So, before determining the right switch for your network, you’re supposed to have a close look at your current deployment and future needs. But for most cases, we recommend you buy Gigabit Ethernet devices instead of Fast Ethernet devices, even if they cost a little bit more. fiber-mart provides a full set of Gigabit switches, including 8 port switch, 24 port switch, 48 port switch, etc. With these high performance Gigabit Ethernet switches, your local network will run faster with better internet speed.

Data Switch vs Hub in a Home Network

Data switches and hubs are common networking devices used to regenerate degraded signals and split a signal into multiple signals. They are handy for splitting up an internet connection to your home network. But do you know how they work in a home network? If they both accomplish the same thing, what’s the difference between a data switch vs hub?
What Is a Data Switch?
A data switch is charged with the job of connecting smaller segments of a single network into a connected whole. It transfers data across a network segment using MAC addresses for reference. Data switches are extensively used in Ethernet local area networks. A data switch operates on the Data Link Layer of the OSI (Open Systems Interconnection) model. This means that data switches are fairly smarter than hubs, as they can route data on a dynamic level. If information is destined for a certain computer, the data switch will only send the data to this computer. This addresses our collision problem as switches use what is called micro-segmentation, which will be elaborated later in this article.
What Is a Hub?
Hub is a network device which controls number of switches and router for the whole network. A hub is a “dumb” device in that it broadcasts whatever it hears on the input port to all the output ports. The good thing about “dumb” devices is that they don’t need much configuration or maintenance. But this leads to collisions between data packets and a general degrading of network quality. If you have a hub set up between your router and the rest of your network, you’re setting yourself up for a huge headache. A hub looks just like a switch, but works differently on the inside. You connect devices to a hub using Ethernet cable and any signal sent from a device to the hub is simply repeated out on all other ports connected to the hub.
Data Switch vs Hub in a Home Network
Data switch vs hub? How do they differ from each other? Hubs are considered Layer 1 (Physical Layer) devices whereas data switches are put into Layer 2 (Data Link Layer). This is where hubs and switches mainly differ. The Data Link layer of the OSI model deals with MAC addresses and switches look at MAC addresses when they process an incoming frame on a port.
Moreover, a data switch is much smarter but pricier than a hub. A data switch can actively manage the connections between the input port and the output ports, so you won’t run into the collision problem or any of the other issues that plague hubs. As you can see below, there are multiple collision domains or segments for the switch network. If computer A and computer B sent data to each other at the same time, you would have a collision. Computer A and computer C or D, however, will not experience a collision in the process. In comparison, for a hub network, there is just one collision domain, which means that if one computer transmits data, it would be interrupted by any of the other computers in the network. Thus, the more devices you connect to the hub, the more collisions there will be in the whole network. The following figure illustrates a data switch vs hub in collision domains.
Data switch vs hub, which one should you choose for a home network? If you purchased the device in question within the last few years, the chance is almost zero that it’s a hub. Historically, switches were expensive and hubs were cheap, but advances in technology have made switches so cheap that they don’t even bother making hubs anymore. Thus, nowadays data switches are higher-performance alternatives to hubs in a home network. fiber-mart provides a full set of high performance data switches, including gigabit ethernet switch, 10gb ethernet switch, 100gbe ethernet switch, etc. If you have any requirement, please kindly visit

The Positive Impact of Using Optical Fibers on Cell Towers

While fiber optic technology has been utilized for many years in the communications industry, consumers generally identify with the role that it plays in wired communications such as Cable TV, Fiber-To-The-Home, and the related networking equipment.  However, what most overlook or do not realize is the significant impact that deploying optical fibers has also had on something consumers use every day – mobile devices.  In order to achieve the high speed data levels that we have become accustomed to when using mobile devices, cell towers and their supporting networks had to be retrofitted with optical fiber cables.
The transition from copper to fiber first started when 3G mobile technology was first introduced, but when 4G LTE technology was deployed, the service providers’ equipment in almost every cell tower had to be upgraded.  The primary reason for this was to support the need for the higher frequencies and faster speeds that the existing 1 5/8 ” coax cables on most cell towers could not handle. Since the primary feed line to most cell towers had been upgraded already, connecting the cell systems in the towers with fiber was the next step.
So what positive changes occurred when transitioning to optical fiber in the cell tower?
First, engineers could now design systems with fiber that run solely off of DC power.  The result was that a very small (less than a ½” in diameter) 16-pair optical fiber cable and two small multi-strand DC cables could replace as many as 12 to 18, 1 5/8” coax cables which are sometimes called “hard lines”.  As you can see, this is a significant improvement.
Secondly, after the hard lines are taken off and replaced with optical fiber cables, both the weight and wind drag are drastically reduced on the cell tower.  The amount of weight and wind drag that is reduced when swapping coax for a fiber-based system is almost unbelievable.  Thousands of pounds of materials are removed and space on the tower is dramatically increased.  In addition to amount of material, a lot of time is saved in comparison to having to add 12 to 18 more hard lines to each system.
By upgrading to incorporate optical fiber cables into the infrastructure, today’s cell towers have realized significant improvements not only in mobile network performance, but also from an architectural standpoint.

Buying Optical Fiber for Network Testing and Latency Applications

When the time comes to buy spools of optical fiber for testing and demonstrating communications systems, there are a few items to consider that will help ensure you end up with an ideal setup.  Since it has been proven that following a few best practices will help you get the most out of your fiber, thinking about these four important items in advance will allow you to further qualify your needs as well as speed up the purchasing process.
1.  Fiber Types & Manufacturers
There are many different optical fibers used in communications networks, so determining the specific type is very important.  Do you need single mode or multimode fiber?  Are you seeking to simulate a field network that requires an exact fiber match, or will an industry-standard equivalent suffice?  Also, keep in mind that both pricing and availability of fiber does vary by type and manufacturer, so you will need to consider this as well during the project planning phase.
2.  Fiber Lengths and Configurations
Once you have selected the appropriate type(s) of fiber, the next step is to determine the lengths needed for your test setup.  Depending upon your solution partner, which we will cover later in this article, there are potentially a number of configuration options available to you.
Will your setup include more “standard” lengths that will apply to many different tests, or will it require very specific lengths like in the case of a fiber latency / optical time delay application?  Is it preferable to use longer continuous lengths, or is having several shorter lengths for distance flexibility more ideal?  Lastly, do you plan to use this fiber for a single set of tests in the short-term, or might it be used for a variety of different tests over the long-term?  (If the latter, it may be beneficial to think about lengths with the bigger picture in mind from a planning perspective)
3.  Enclosure Type
In terms of enclosures for your fiber spools, there is no question that you should always utilize them, since there are too many risks related to using unsecured and unprotected spools.  From the cost of replacing broken fibers and the potential for unreliable test results, to your setup looking sub-standard versus a competitor who did follow this best practice, this is an absolute must and a solid investment.
At a high level there are two primary categories, portable and rack-mount, which than have many variations.  This is fairly straightforward as each has its respective advantages, so your decision is based solely upon the preferred setup for the application/environment.
Depending upon the solution vendor you decide to partner with, there may be more or less enclosure options available to you.  In many cases, the length configurations you have determined will help to narrow down the types of enclosures that a given vendor can provide from their portfolio to meet your needs.
4.  Solution Partner / Vendor Selection
Since the leading fiber manufacturers focus on mass production of standard lengths and do not provide enclosures, selecting a proven solution partner that specializes in selling fiber as part of a quality testing platform is important.  While it may seem like installing a spool of fiber in an enclosure is simple, working with bare fiber is not easy.  It requires well-designed hardware, skilled professionals, specialized equipment, and very hands-on processes to ensure a great finished product.
Important Note:  It takes time for even the most qualified vendors to build and deliver these types of quality platforms, from fiber availability through time/labor for careful spooling, assembly, and testing procedures.  Therefore, it is always recommended to plan in advance and not wait until last-minute when seeking to acquire fiber.
It can be very detrimental and costly if this aspect is overlooked and/or if cost is the only driving factor when choosing a vendor.  Experience, capabilities, available options, and services are all key factors to inquire about and review during the selection process.
In conclusion, by taking all of these considerations into account prior to making a fiber purchase, it will go a long way to ensuring your setup will provid maximum value to your organization, while making the entire process easier.

Why PONs is Important to Test Them Before Deployment

The fact that fiber optics are used in the transmission of light-signal data is widely known, as is the fact that separated ways are required to allow those signals to arrive at their intended destination. Typically speaking, there are two types of network that are employed to achieve this goal:
Active Optical Networks (AONs)
However, in this article, we focus on the latter and why it’s vital to perform testing on these passive networks before they’re officially deployed.
Passive Optical Networks Defined
In the modern day, huge investment is being put into access networks by service providers to meet the ever-growing high-bandwidth broadband demand. These same server providers prefer to see an evolution of technology, as well as longevity, to meet future demand, which is why the use of PONs is being seen more and more frequently.
PON is a technology used in telecoms to implement a point to multipoint architecture, and it can serve numerous endpoints from a single optical fiber, through the use of unpowered splitters. The net result of this system (which could be referred to as FTTH (fiber to the home), FTTB (fiber to the building) or FTTC (fiber to the curb)) is that each customer no longer needs to be connected to the hub by separate fibers.
A typical PON is comprised of multiple ONUs (optical network units) and an OLTs (optical line terminations). Generally, an OLT is located at the central office of the server provider, with as many as 32 ONUs situated close to the end users. The ‘passive’ part of the nomenclature refers to the fact that while the optical signal is traversing the network, there are no active electronic parts, and no power is needed.
In FTTH, a PON system allows for costly hardware components to be shared, as a splitter can take a single input and separate the signal to transmit to multiple users. This sharing can result in cost savings to the service provider, especially as splitters can send signals in both directions, from the central office to the users and vice versa.
Optical Splitters
A PON uses non-powered optical splitters to separate signals as they progress through the network, sharing strands of fiber optics for different parts of network architecture. Because PONs only require power at the transmitting and receiving ends of the network and can serve up to 32 users with a single strand of fiber, they offer an option that’s both cheaper to build and to maintain than an AON. (Research Gate Mar 2018)
That’s not to say that PONs are perfect, as they have a few disadvantages – namely that they have a shorter range than an AON and when an outage occurs, it’s trickier to isolate the issue. Also, as bandwidth is shared between subscribers in a PON, the speed of data transmission can drop at peak times of the day, which can cause issues to smooth service use.
The Benefits of a PON
PONs came into mainstream use back in 2009, as they were designed as a way of connecting homes to internet, telephone and TV services en masse. The reason they became so popular is that they come with several benefits:
● Reduced operational costs
● Lower installation costs
● Reduced network energy costs
● A reduction in required network infrastructure
● No requirement for network switches
● IDF real estate can be reclaimed
When a PON is deployed, it will typically replace large bundles of legacy copper wiring with a much smaller and more manageable and cheaper to maintain single mode fiber cable. This allows for greater distances between desktop and data center (up to 20km), and it represents a much more secure option than copper, as it’s more difficult to tap and encryption occurs between the ONT and OLT.
Importance of Testing Before Deployment
Before a PON is deployed, it’s vital that its installation is properly tested as, to meet the client’s expectations, the reflectance levels inside the fiber need to be within acceptable parameters. If proper testing isn’t conducted and an excess of reflectance and signal loss within the network is allowed to persist, it can lead to serious performance issues.
A practical method of testing a PON often involves using OTDR (Optical Time Domain Reflectometry) equipment, which passes the wavelength frequency to be used through the network so that any issues are immediately highlighted. (Building Industry Consulting Service International (BICSI) 2018)
In Conclusion
While PONs have existed in the telecoms industry for many years, they are, at last, being used at an enterprise level in healthcare, education and a host of other sectors, offering new opportunities for new, low-cost, low-maintenance infrastructures. Of course, there will be instances where AONs may be more appropriate, but fully-tested PONs and what they offer is finally (and rightly) being seen as a viable alternative to their more expensive, powered counterparts.

CWDM System Testing Process

With the explosion of CWDM, it is very necessary to formulate a basic testing procedure to certifying and troubleshooting CWDM networks during installation and maintenance. Today, one of the most commonly available test methods is the use of an OTDR or power source and meter, which is capable of testing the most commonly wavelengths, 1310, 1490, 1550 and 1625nm.
This article here is based on the pre-connectorized plug and play CWDM systems that allow for connecting to test equipment in the field:
In the multiplexing module of a pre-connectorized CWDM system, wavelengths are added to the network through the filters and transmitted through the common port. The transmitted wavelengths enter the COM port in the de-multiplexing module and are dropped. All other wavelengths present at the MUX/DeMux module are went through the express port.
Most of today’s OTDRs have expanded capability for testing wavelengths in addition to 1310 and 1550 nm. The OTDR allows partial testing of such system offered in test equipment source. The OTDR allows partial testing of these systems by using the flexibility of pre-connectorized solutions. This is done by switching connections within the CWDM field terminal to allow for testing portions of the non-1310/1550 nm optical paths.
To test the 1310nm, the first step is to test the downstream portion of a system at 1310 nm by connecting the OTDR to the 1310 nm input on the CWDM MUX located at the headend. Then switch the test leads over the the upstream side and repeat. Test method is the same for both the downstream and upstream paths.
1550 nm testing is performed similarly by switching the test leads to the 1550nm ports. If additional wavelengths are present, you need to follow the procedures below:
Using the 1550 nm test wavelength, switch the OTDR connection to the 1550 nm input port on the headend MUX. Have a technician stationed at the field terminal connect the drop cable leg connectors for the 1570 nm customer to the 1550 nm port on the Mux/demux device. What should be noted is that in a play and plug solution this should not require repositioning where the drop cable passes through the OSP terminal. Test the downstream 1570 nm passive link at 1550 nm, and then repeat for the 1570 nm upstream side. When testing is complete, have the technician switch the connections for the 1570 nm drop back to the 1570 nm ports on the field MUX/DeMUX device as shown in Figure 6. Repeat this process for the 1590 nm, 1610 nm drop cables and other wavelengths present. Finally, test the 1550 nm path normally with the 1550 nm drop cable connected to the 1550nm MUX/DeMUX ports.
Since the OTDRs is able to test at 1490 or 1625 nm, the drop cables under test could be connected to the EXP port of the module and tested at 1490 or 1625 nm respective wavelength, without having to connect each to the 1550 nm port. Otherwise the procedure is the same.
As CWDM network become more and more common the data they carrying has also become critical. The procedure introduced here allows for testing modular pre-connectorized CWDM systems with standard optical test equipments. Relative channel power can be measured with a wide-band fiber optic power meter at the filter outputs or at other points in the network with the aid of a wavelength selective test device or with an optical spectrum analyzer.