Active alignment:
The process of aligning optical components in which the power of the optical signal is monitored and maximized before the components are finally attached. Assembly thorugh active alignment is a significant source of the cost of today's optical components.
Application Specific Integrated Circuit (ASIC):
A silicon chip that is custom-designed for a particular purpose, at least that's the pure definition. In actuality, the terms is misleading because many ASICs are designed to perform multiple, generalized tasks. From the manufacturer's point of view, a microprocessor is an ASIC, though they can and are used for widely disparate purposes in the field. An ASIC requires large production volumes to be economical; long design cycles and high-priced design tools (and designers) make them expensive to create, but inexpensive to product in high-volumes. Manufacturers use ASIC to consolidate many chips into a single package, thereby reducing system board size and power consumption. Many video boards and modems use ASICs. ASICs span programmable array logic (PAL) devices, electrically programmable logic devices (EPLDs), field programmable logic devices (FPGAs), gate arrays, standard cell-based devices, and full custom, designed-from-scratch ICs.
BiCMOS (also called BiMOS)
Channel:
A wavelength of light that carries data. Optical fibers and waveguides can carry multiple simultaneous channels, increasing their information capacity.
Coherent light:
A beam of light whose photons all have the same optical properties (wavelength, phase, and directly). Coherent light is important for communication because it travels much farther in optical fiber without distortion.
Complimentary Metal Oxide Semiconductor (CMOS):
A widely used type of semiconductor technology that uses both NMOS (negative polarity) and PMOS (positive polarity) circuits. Since only one of the circuit types is on at any given time, CMOS chips require less power than chips using just one type of transistor.
Data Communications (Datacom):
The transfer of data between points. This includes all manual and machine operations necessary for this transfer. In short, the movement of encoded information by means of electrical transmission systems.
dB (Decibel):
Usually used as a figure of loss or gain in an optical network. This is calculated as one-tenth of the logarithm of the output power divided by the input power. A gain of 3dB gain represents an increase of 100 percent.
Demultiplexing:
The process of separating different wavelengths from a fiber utilizing multiple data channels. This is the opposite of multiplexing.
DWDM:
Dense Wavelength Division Multiplexing. DWDM is the higher-capacity version of WDM (Wavelength Division Multiplexing)
Electromagnetic Interface (EMI):
Interference in signal transmission or reception caused by the radiation of electrical and magnetic fields. That's the easy explanation. Here's a more comprehensive explanation: Any electrical or electromagnetic phenomenon, man made or natural, either radiated or conducted, that results in unintentional and undesirable responses from, or performance degradation or malfunction of, electronic equipment.
Electo-optic (also called optoelectronic)
Fiber/Optical fiber:
Very thin strands of pure silica glass through which laser light travels in an optical network. Optical fibers are used to bring light onto and off a silicon optical chip. The core of the fiber can range from 6 to 125 microns. For reference, the diameter of human hair ranges from about 80 to 100 microns.
Field Programmable Gate Array (FPGA):
A user-configurable logic device in the form of a microprocessor. FPGAs comprise a mind-boggling variety of devices which contain memory that holds user-defined logic constructs and interconnects. Memory technologies include EEPROM, EPROM, FLASH EPROM, SRAM, fuse elements (mainly in lower density devices), anti-fuse elements, and laser-etched metal. The memory types defines whether the configuration is maintained when power is removed (EEPROM, EPROM, FLASH, fuse, antifuse, and etched metal versions) or whether the configuration must be reloaded on during power-on (SRAM versions). Fundamental design trade-offs include the complexity of the basic cells (usually a 3-5 input look-up table and flipflop) and the richness of routing resources available to connect between cells. Modern FPGAs also include various types of signal compatibility (differential and/or low voltage inputs and outputs) and user-memory elements (either distributed or provided as array blocks). Modern designs allow the placement of preconfigured logic (microcontrollers, FOFOs, RISC processors, UARTS) for complete SOCs (system-on-chips). FPGAS [sic] are available with huge amounts of logic (up to 5 million gates announced) and pin counts (24-500+ pins). This area of technology is very dynamic and exciting. Thanks to Ken Coffman for this definition. Ken literally wrote the book on ÒReal World FPGA Design with Verilog.
Frequency:
The number of cycles of an electric signal per unit time, measured in Hertz (Hz). Frequency can be used to describe the lightwave itself and also to describe the rate of data modulation applied to a lightwave.
Gallium Arsenide (GaAs):
An exotic semiconductor compound used for making electronic and optoelectronic devices.
Gbps, Gb/s (Gigabit per second):
1 Gb/s is 1 billion bits of data per second.
Gigahertz (GHz):
Hertz describes the number of times an electrical signal completes a full cycle in one second. 1 GHz means the signal has changed cycles one billion times in one second.
Grating:
A device used to separate different wavelengths. A grating can be used as a wavelength filter (see filter). By changing parameters of the grating (e.g. thermal tuning, or electical tuning) the wavelength that is filtered can be changed.
I2C:
Inter-Integrated Circuit, with I2C actually meaning I^2C as in I Squared C. A bidirectional, two-wire, serial bus specification developed in the early 1980's by Philips Semiconductors to provide a communications link between integrated circuits for audio and video (e.g., TV sets and VCRs) equipment. I2C now extends to a wide variety of computer peripherals such as keyboards, mice, printers, and monitors. I2C is a multi-master bus, meaning that multiple masters can initiate data transfers over the shared bus, with a arbitration mechanism determining which master has priority at any given time.
Indium Phosphide (InP):
An exotic semiconductor compound used from making electronic and optoelectronic devices.
Infrared:
The region of the electromagnetic spectrum between red light and radio waves. This includes all wavelengths that are used in optical networks. Silicon is transparent to most infrared wavelengths used in optical communications, typically wavelengths from 130 to 1610nm.
Integrated Circuit (IC):
After the transistor and other solid state devices were invented, electronic circuits were designed that were more complex than ever. It became a real problem wiring all the components together. In 1958-1959, Jack Kilby and Robert Noyce independently invented the integrated circuit. An integrated circuit is a piece of silicon or other semiconductor called a chip on which is etched or imprinted a network of electronic components such as transistors, diodes, resistors, etc. and their interconnections.
Interconnect:
An electrical or optical connection (or cable) connecting two devices. Examples of interconnects are the cable to connect a computer monitor to the computer, or the cable between the computer and the disk drive. There are many of these interconnects inside a typical computer. Interconnects can also be found connecting chips on a circuit board.
Laser:
Strictly speaking, Light Amplification through Stimulated Emission of Radiation. Today, a laser is considered to be any device that emits an intense, coherent beam of light (see Coherent light). Coherent light can carry data over great distances in optical fiber without distortion.
Limiting Amplifier (LA):
Relating to analog signals and their processing. Also refers to the operating range of an amplifier where little or no distortion occurs.
Mach-Zehnder Interferometer (MZI):
In general, an interferometer that splits an optical signal into two components and directs them down two separate paths, then recombines them. By inducing a phase delay between the two optical signals, the resulting interference can cause intensity changes. Such a device can modulate the optical power from 100% (constructive interference) to 0% (destructive interference).
Mbps (Megabits per second):
1 Mbps is 1 million bits per second
MHz (Megahertz):
1 MHz means the signal has changed cycles one million times in one second.
Micrometer/Micron:
A measure of length: 1 um = 0.000001 meter (millionth of a meter).
MIMIC
Modulation/Modulator:
A modulator is a device that encodes data onto a beam of light at extremely high data rates by acting like a switch to turn the light off and on, similar to the way a transistor acts like a switch to turn the flow of electrons on and off.
Multiplexing:
The combing of different wavelengths in a wavelength-division multiplexing system. By multiplexing different wave wavelengths in a single channel, the bandwidth or amount of information that can be transmitted per unit time is increased, much like a five lane highway supports more traffic than a single lane highway.
Nanometer (nm):
A nanometer is a measure of length. 1 nm = 0.000000001 meter (1 billionth of a meter). It is about 70,000 times smaller than the width of a human hair.
Optical Amplifier:
A device that boosts an optical signal's intensity directly without performing an expensive optical-to-electrical signal conversion. Optical amplification extends the distance the signal will travel before it fades away.
Optical Modulator:
An active optoelectronic component, typically [except the GigOptix TFPS Modulators] made from lithium niobate or gallium arsenide, that turns an optical signal on and off to encode and transmit data throughout the network. Modulation can be achieved directly by tuning a source laser on and off or externally by altering a continuous source laser signal to achieve a similar on/off effect. Long-distance and submarine optical networks typically use higher-power lasers and external modulators, while shorter-distance optical networks are better suited for direct modulation.
Phase shift:
A change in phase of a periodic signal with respect to another periodic signal or reference signal. Inducing a phase shift is at the heart of the Mach-Zehnder interferometer used in optical modulators.
Photodetector/Photodiode:
A device that converts optical signals (photons) into electrical signals (electronics). A photodiode is used to read data from an optical fiber and send information to electronic devices.
Photon:
the quantum unit of electromagnetic radiation. The elementary "particle" of light.
Photonics:
The technology of transmission, control, and detection of light (photons). This is also known as fiber optics and optoelectronics.
PIN:
A diode made from an intrinsic (un-doped) region surrounded by a p-doped and an n-doped region, hence P-I-N.
Polymer:
A polymer is a chemical compound. It is organic, meaning that it is carbon based, such as cellulose, gelatin, and plastic. It is called a polymer because it is made up of many repeated simpler units or monomers. Polymers have high relative molecular mass, the structure of which essentially comprises the multiple repetitions of units derived, actually or conceptually, from molecules of low relative molecular mass. A polymer made entirely from molecules of one monomer is referred to as a "homopolymer". Chains that contain two or more different repeating monomers are "copolymers". The resulting molecules may be long, straight chains, or they may be branched, with small chains extending out from the molecular "backbone". The branches also may grow until they join with other branches to form a huge, three-dimensional matrix. Variants of these molecular shapes are among the most important factors in determining the properties of the polymers created.
Raman Effect:
A process by which light interacts with vibrating atoms in a material, resulting in the transfer of energy to different wavelengths. In silicon, this effect is about 10,000 times stronger than in glass fiber.
Receivers:
Devices placed at the end of an optical network with detectors to convert the lase light back into electrical form. In other words, converting the photons to electrons.
Refractive index:
A property of a material that determines how fast light travels through it.
Silica:
Very pure glass from which optical fibers are manufactured; a combination silicon and oxygen (SiO2).
Silicon:
The most common semiconductor for building integrated circuits, including microprocessors. Silicon can also be used to me photonic devices. The Raman effect in silicon is 10,000 times stronger than in glass fiber.
Silicon Photonics:
Technology of making optical devices using silicon and standard CMOS manufacturing techniques.
Small Form Factor (SFF)
Splitter:
An optical device, typically a waveguide, designed to split an optical signal into two components.
System-on-Chip (SoC):
If you put digital signal processing, microprocessing, network, memory-and maybe seven some analog-functionality on one chip, you can dramatically lower power, cost, and real estate. And increase performance. . . . SoC places the contents of many integrated circuits - microprocessors, memory, logic and embedded software – into a single semiconductor chip. In more technical language, a SoC is a silicon integrated circuit which combines generic functions (e.g., microcontrollers, UARTs, memory, FIFOs, and other analog and digital logic functions) with custom design elements to create a device that contains all major elements of a system on one integrated chip. This is on method of increasing design productivity. The SoC designer collects and integrates pre-defined (and pre-tested) components similar to the way hardware designers collect and interconnect integrated circuits on a circuit board design. The final implementation of an SOC may be in an ASIC or FPGA.
Taper:
A section of a waveguide or optical fiber that is tapered to allow for more efficient coupling into/out of a device. A taper is commonly used to minimize the amount of light lost between two optical elements, e.g. between a laser and a waveguide, or between a waveguide and an optical fiber.
Telecommunications (Telecom):
1. The art and science of communicating over a distance by telephone, telegraph and/or radio. The transmission, reception and the switching of signals, such as electrical or optical, by wire, fiber, or electromagnetic (i.e. through-the-air) means. 2. A fancy word for telephony, which it replaced and which many thought meant only analog voice, but didn't.
THz (Terahertz):
A teraherz is 10^12 hertz or a thousand gigahertz, a measure of frequency. At one terahertz, each cycle is one picoseoncd, and the wavelength in free space is roughly 300 micrometres. Radio waves sent at terahertz frequencies usually travel in line of sight. These waves, known as terahertz radiation, are in a waveband that is the overlap of what is normally regarded as microwave radiation and far-infared light. The Earth's atmosphere is a strong absorber of terahertz radiation, so the range of terahertz radiation is quite short. However, recent technologies using terahertz radiation have been developed, which are intended for applications such as medical imaging and surveillance.
Transceiver:
1. Any device that transmits and receives. In sending and receiving information, it often provides data packet collision detection as well. 2. In IEEE 802.3 networks, the attachment hardware connecting the controller interface to the transmission cable. The transceiver contains the carrier-sense logic, the transmit/receive logic, and the collision-detect logic. 3. A device to connect workstations to standard thick Ethernet-style (IEEE802.3).
Transimpedance Amplifier (TIA) (also known as Current-to-Voltage Converter)
Transmitters:
Devices placed at the beginning of an optical network to transmit light representing information. Usually consists of laser and modulators. In other words, converting electrons to photons.
Transponder:
1. A transponder is a fancy name for radio relay equipment on board a communications satellite. Just like its domestic microwave counterpart (which you see along highways), a transponder will receive a signal, amplify it, change its frequency and then send it back to earth. On a satellite transponder that uses frequency modulation, the bandwidth required for an analog tv [sic] signal is 27Mhz. Since satellites are power limited, FM is the analog modulation of choice. In exchange for wide bandwidth and poor spectral efficiency, FM offers improved signal-to-noise ratio. On a terrestrial TV station or cable TV network where power is not an issue, amplitude modulation is used which offers better spectral efficiency so that bandwidth needed for an analog TV signal is only 6Mhz. 2. A transponder on an airline is a slightly different kettle of fish. When a radar signal strikes a airline, it activates an electronic transmitter called a transponder. The transponder sends out a coded signal to the ground radar. The code appears next to the radar image of the plane, allowing the controller to identify each plane under his control. Newer aircraft have automatic collision avoidance systems that will change the fight path of two or more planes if they appear to the systems as though they're going to crash.
Two-photon absorption:
A quantum mechanical process by which photons that would normally pass through an atom are instead absorbed because two photons arrive simultaneously with enough total energy to free an electron from the atom. This process can quickly generate free electrons in silicon, which can absorb even more light, and thereby counteract Raman amplification.
Waveguide:
Guides light on a wafer in a way similar to optical fiber, acting like the optical equivalent of wires connecting different devices. These waveguides are constructed on silicon wafers by etching very precise silicon channels on the wafers. Through precise manufacturing, waveguides can be manufactured that will split the light into two beams (splitter), or the waveguides can be manufactured to focus the light into a narrower beam, (a taper).
Wavelength:
the distance between successive crests of waves. All electromagnetic radiation (radio waves, microwaves, ultraviolet light, visible light, etc.) is transmitted in waves. In optical networks, different wavelengths are different colors of light.
Wavelength conversion:
The process of taking light of one wavelength (color) and changing it to another wavelength (color). In communications, more data can be transmitted by sending multiple wavelengths of light down the same optical fiber. Wavelength conversion allows the switching of data from one wavelength to another. The Raman effect is silicon can produce such a wavelength conversion.
Wavelength-Division Multiplexing (WDM):
Transmitting many different colors (wavelengths) of laser light down a single fiber. By multiplexing, the bandwidth-or amount of information that can be transmitted per unit of time-is increased, much like a five-lane highway can support more traffic than a single-lane highway.
Thank you to Wikipedia; Newton, Harry (2005). Newton's Telecom Dictionary: 21st Updated and Expanded Edition. San Francisco: CMP Books.; and our own GigOptix Engineers for the definitions.