Category: Fiber Transceivers

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

What is a Direct Modulated Optical Transmitter

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 Today, let’s learn about a optical transmitter, especially called Direct Modulated Optical Transmitter equipment via three topics: working principle, products preview and Performance Features.
Working Principle
 Modern fiber-optic communication systems generally include an optical transmitter to convert an electrical signal into an optical signal to send into the optical fiber, a cable containing bundles of multiple optical fibers that is routed through underground conduits and buildings, multiple kinds of amplifiers, and an optical receiver to recover the signal as an electrical signal. The information transmitted is typically digital information generated by computers, telephone systems, and cable television companies.
  Laser is the most expensive machine components, machines equipped with microprocessors. The microprocessor software to monitor the working state lasers, operating parameters from the panel LCD display. Once the laser operating parameters deviate from the permissible range set by the software, the microprocessor will automatically turn-off laser power. Flashing yellow light prompts alarm panel LCD prompts cause of the malfunction (non-human factors that can not be damaged laser). RF pre-distortion technology, ensuring the case of CSO-performance system for maximum CNR.
FOT series Optical Transmitter products adopt the high linearity, optical isolation, the DFB, thermoelectric cooling DFB laser produced by ORTEL 、AOI、Fujitsu、Mitsubishi and other world-renowned semiconductor companies. It can provide high-quality images, digital or compressed digital signal long-distance transmission for cable television and telephone communications. Built-in RF driver amplifier and control circuitry to ensure the machine’s CNR, CTB, CSO target. Comprehensive and reliable optical circuits and laser output power stability Temperature stability of thermoelectric cooler control circuit to ensure optimal machine performance and long-life laser stability.
Quality: original system optimization control technology and RF pre-distortion technology ensure that the system can acquire the maximum CTB, CSO, and SBS targets in the case of excellent performance CNR.
Reliability: The 19 “1U standard rack, built-in high-performance dual switching power supply,it can work in the backup at 85 ∽ 265Vac City Network Voltage, MS-level automatic switching; chassis cooling automatic temperature control.
Intuitive: The laser is the most expensive machine components, machine equipped with microprocessor monitors the working state of the laser, the panel LCD window displays the operating parameters. Once the laser operating parameters deviate from the permissible range set by the software, micro-processing will automatically turn off laser power, yellow light goes on to warn, the panel LCD prompts the cause of troubles.
Power plug: Aluminum structure using plug switching power supply, allows for heat dissipation and replacement. And dual power supply hot and cold backup.

Learn about EDFA equipment in few minutes

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WDM EDFA used to combine CATV signal from optical transmitter with internet signal from OLT and output to single fiber.
EDFA product overview
An Erbium-Doped Fiber Amplifier (EDFA) is a device that amplifies an optical fiber signal (from CATV). An WDM EDFA is used to integrated 1550nm CATV (optical signal) and 1490nm /1310nm data stream from the PON into single fiber transmission.
FOT EDFA series of products adopt 980nm or 1480nm high linearity, optical isolation, the DFB, thermoelectric cooling DFB laser produced by JDS, Fujitsu, Nortel, Lucent, Fitel and other world-renowned semiconductor companies as the pumping source.
In the interior of the machine is equipped with the light power export stable circuit and laser Thermoelectric cooling device Temperature stability control circuit to ensure optimal machine performance and long-life laser stability. The microprocessor software monitor the lasers’ working state, the Digital Panel (VFD) displays the operating parameters. Once the laser operating parameters deviate from the permissible range set by the software, micro-processing will automatically turn off laser power, red light goes on to warn, digital panel prompts cause of troubles., a detailed report of the device parameters please read FOT EDFA user manual.
EDFA and optical communications
EDFA (Erbium Doped Fiber Amplifier) is a representative one in the optical amplifier. As the EDFA’s wavelength is 1550nm, it is in line with the low-loss band of fiber and its technology has been relatively mature, so widely used.
Erbium-doped fiber is the core components of the EDFA, it makes quartz optical fiber as matrix material, and incorporate a certain proportion of rare earth element erbium ions (Er3 +) in the core of a fiber. When certain amount of pump light is injected into the erbium-doped fiber, Er3 + have been excited from the low-energy level to the high energy level, due to Er3 + has a very short lifespan on the high energy level, and soon transit to a higher level by the form of a non-radiative, and form the population inversion distribution between this energy level and low-energy-level. Because the energy between these two energy levels is exactly equal to the photon energy of 1550nm, stimulated emission of 1550nm light can only occur, we can only enlarge 1550nm optical signal.
EDFA has revolutionized optical communications
All optical and fiber compatible
Wide bandwidth, 20~70 nm
High gain, 20~40 dB
High output power, >200mW
Bit rate, modulation fromat, power and wavelength insensitive
Low distortion and low noise (NF<5dB)
Basic principle of EDFA
A relatively high-powered beam of light is mixed with the input signal using a wavelength selective coupler. The input signal and the excitation light must be at significantly different wavelengths. The mixed light is guided into a section of fibre with erbium ions included in the core. This high-powered light beam excites the erbium ions to their higher-energy state. When the photons belonging to the signal at a different wavelength from the pump light meet the excited erbium atoms, the erbium atoms give up some of their energy to the signal and return to their lower-energy state.
A significant point is that the erbium gives up its energy in the form of additional photons which are exactly in the same phase and direction as the signal being amplified. So the signal is amplified along its direction of travel only. This is not unusual – when an atom “lases” it always gives up its energy in the same direction and phase as the incoming light. Thus all of the additional signal power is guided in the same fibre mode as the incoming signal. There is usually an isolator placed at the output to prevent reflections returning from the attached fibre. Such reflections disrupt amplifier operation and in the extreme case can cause the amplifier to become a laser. The erbium doped amplifier is a high gain amplifier.

The release of Draft Specification for Next Generation 100Gbps Optical Interconnect Systems

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Recently, 100G Lambda Multi-Source Agreement (MSA) Group announces the release of draft specifications based on PAM4 optical technology at 100 Gbps per wavelength. Member companies at MSA address the technical challenges of implementing optical interfaces with 100 Gbps per wavelength PAM4 technology and multi-vendor interoperability for optical fiber manufacturers of varying manufacturer and form factor variations . The goal of this new optical specification is for next-generation network devices that, on demand, will need to meet the industry’s growing demand for higher bandwidth and bandwidth density.
100G Lambda MSA team members include: Alibaba, Applied OptoElectronics, Arista Networks, Broadcom, Infocomm, Cisco, Phoenix, Hong Teng Precision Technology Co., Ltd., Inphi, Intel, Juniper Networks, Lumentum, Luxtera, Magnesium Microwave Technology, MaxLinear, Microsoft, Molex, Synaptic, Nokia, Orlano, Semtech, Saul Optoelectronics, and Sumitomo Electric.
The 100G Lambda MSA-defined new interface increases the distance between 100 GbE and 400 GbE applications over the 500m transmission distance interface currently defined by 100 Gbps (100GBASE-DR) and 400 Gbps (400GBASE-DR4) as defined by the IEEE 802.3 Ethernet standard . Optical specifications developed for 100 GbE at 100G Lambda MSA can achieve transmission distances of 2 to 10 kilometers and optical specifications developed at 400 GbE can achieve transmission distances of up to 2 kilometers on duplex single-mode fiber. The 100G Lambda MSA focuses primarily on 100 Gbps per wavelength and enables a complete ecosystem of technologies for the next generation of network equipment.
 The 100G Lambda MSA specification is available at their website 100GLambda. It is expected that MSA Group will complete the full set of specification development by early 2018. Companies will be invited to join the league as contributing members.

Benefits of Using Fiber Optic Attenuators with Doped Fiber

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Fiber optic attenuators are used in networking applications where an optical signal is too strong and needs to be reduced. There are many applications where this arises, such as needing to equalize the channel strength in a multi-wavelength system or reducing the signal level to meet the input specifications of an optical receiver. In both scenarios, reducing the optical signal strength is necessary or else system performance issues may arise.
Types of Fiber Optic Attenuators
There are many forms which can be taken by optical attenuators, but the two basic types of fiber optic attenuators are fixed and variable. In this article, we will focus on the fixed type.
The size of the build out attenuator is approximately 1.25 inch. Many have a male interface connector at one end and a female interface connector at the other end but female to female interface connectors are also available. The fabrication of the build-out style is typically accomplished using with air gap attenuation or doped fiber attenuation.
What are Air Gap Attenuators?
Air gap attenuators accomplish the loss of optical power with the help of two fibers that are separated by air to yield the loss. These attenuators can be fixed or variable, but a downside is that they can be vulnerable to dust contamination and are also vulnerable to changing temperatures and moisture. One must also be cautious where they are used. For example, multi-channel analog systems, like ones used by CATV, this attenuator can create second order distortions that reduce the performance of the system.
What are doped Fiber Attenuators?
As the name suggests, doped fiber attenuators consist of a small fiber piece along with metal ion doping which provides the exact attenuation and interfaces in between female and male connections on the attenuators. These types can be wavelength sensitive because of their fabrication. The primary reasons why these doped fiber attenuators are preferred include:
Not susceptible to dirt, moisture, or temperature variations
Provide a stable performance over wide wavelength variations and band passes.

Eliminate the “Dead Zone” With an OTDR Launch Box

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The Optical Time Domain Reflectometer (OTDR) is a vital tool for fiber optic testing that can analyze the performance of fiber optic cabling through the use backscattering technologies, as well as identifying and locating connectors, splices, and breaks in fiber optic networks.
However, there is an unwanted phenomenon known as ‘dead zone’ that occurs when using an OTDR, which can cause improper readings if the right steps aren’t taken. This dead zone limitation can be avoided through the use of an OTDR Launch Box, which is what we review in more detail here.
The Launch Box Basics
The launch box, which is also known in the industry as a launch fiber, pulse suppressor, dead zone box or fiber ring, is a device that helps to eliminate the dead zone issue during fiber optic testing significantly. The dead zone is something that occurs when the pulse width changes and causes a high degree of reflection that can cover an area several hundred meters from where the OTDR is located. This results in the OTDR device not being able to detect events or issues in that area.
A term launch box is a box that contains a long spool of fiber that is placed in between the fiber being tested and the OTDR. This provides extra fiber on which the dead zone can occur. This enables the OTDR to now detect events at the beginning of the fiber being tested.
Using Your Launch Box
Launch boxes come in various shapes and sizes. However, all tend to have a robust outer casing to make them more durable. Each end of the fiber is terminated, with one to be attached to the OTDR and the other to the fiber being tested. Once connected to the relevant ports, the test can be run accordingly.
While using an OTDR box is a relatively simple process, you must be sure that it contains a sufficient length of fiber to take account of the entire dead zone or you still won’t achieve a proper reading on your trace and could miss events. Choosing the right OTDR launch box is important, as they can be customized to the specific application or device.
hoosing the Right One
When choosing the right OTDR launch box for your needs, you should approach it in the same way as you would choose a fiber patch cable. Box styles along with features such as connector type, fiber type, and fiber length should all be determined. Furthermore, some launch boxes are available with bulkhead adapters while others provide directly terminated fiber ends.
As mentioned before, a dead zone can cover several hundred meters, so your launch box spool should be long enough to cater for this. It is important to make sure you choose one that suits the job, and your OTDR user manual can provide guidance regarding the expected dead zones.

Fusion or Mechanical: Which Is the Best Splicing Method?

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When splicing together two lengths of fiber optic cabling, you have to choose between the two known methods – fusion splicing and mechanical splicing – which both essentially produce the same result – a secure connection between two formerly separate lengths of fiber.

However, how do you choose between them? Is one method better than the other? Well, in this article, we take a closer look at both, to provide some clarity on the subject. By reading to the end, you’ll know what the pros and cons are of each, how each connection is created and you’ll be in a better position to make a considered decision.

So, without any further delay, let’s begin.

Defining Mechanical & Fusion Splicing

The ultimate goal of cable splicing is to create a secure connection between two or more sections of fiber in a way that allows the optical signal to pass through with minimal loss. As we mentioned already, both mechanical and fusion splicing achieve this goal, but they do so in very different ways.

Fusion Splicing

Firstly, fusion splicing involves melting the two sections of fiber permanently together. This is achieved with an electrical device aptly known as a fusion splicer, and it’s something that not only melts the two parts together with an electric arc, but it is also able to align the fiber to create a good connection precisely.

Mechanical Splicing

One of the main differences with mechanical splicing is that it doesn’t permanently join the fibers together, instead of locking and aligning the pieces together with a screw mechanism. This method requires no heat or electricity at all.

The Fusion Splicing Steps

Figure 2: fusion splicer showing fiber positioning

With both mechanical and fusion splicing techniques, there are four distinct steps to the process. The first two steps for each are almost identical, but the final two are where the differences lie.

Fusion Splicing Step 1 – Preparation

To prepare the fiber for splicing, you need to strip away the jacket or sheath that surrounds the internal glass fiber. You’ll be left with bare glass when you’re finished, which should then be cleaned with an alcoholic wipe.

Fusion Splicing Step 2 – Cleaving

The next step involves cleaving the fiber, which shouldn’t be confused with cutting. Cleaving means that the fiber should be lightly scored and then flexed until it naturally breaks. To create a sound connection, you need a good, clean, smooth cleave that’s perpendicular to the fiber it’s being connected to in the fusion splicer.