OSA DWDM Comparison
The emergence of high-speed DWDM systems has sped the development of more powerful optical spectrum analyzers (OSAs). These instruments can ensure proper system operation, characterize individual components and monitor performance.
OSAs use diffraction gratings to separate light into its component wavelengths and measure power for each. They provide results in graphic form with wavelength on the horizontal axis and power on the vertical axis.
DWDM Technology
Dense wavelength division multiplexing (DWDM) is a crucial component of optical networks that allows data transmission at high speeds. It is the underlying technology that transmits voice, video-IP, ATM, and SONET/SDH.
DWDM is deployed in many different systems, including metropolitan area networks (MANs), and it can be deployed in a variety of different topologies. Typical topologies include a meshed ring, where every site can communicate with every other site, and a hubbed ring, which includes a hub node and satellite nodes.
Because DWDM uses very narrow spectral windows, it is important to use closely spaced optical amplifiers in order to optimize network capacity. This means that the amplitude transfer function of these systems is very narrow, typically from 1525 to 1570 nm. This narrow bandwidth enables designers to exploit as many carriers as possible.
However, this narrow window also means that the spacing between the optical amplifiers used in DWDM networks must be as small as possible. This is the reason why many wdm system providers have recently introduced systems with channel intervals as small as 100 GHz.
This has led to the need for new test equipment that can be used to monitor and measure these closely spaced channels. This is where optical spectrum analyzers (osas) and multiwavelength meters (mwms) come in.
Osas work by filtering incoming light through a diffraction grating. The grating’s density, the distance from the detector, and the optical circuit configuration combine to determine the osa’s wavelength resolution.
The osa can be configured to measure all the wavelengths that are used in a single DWDM channel or to separate closely spaced channels and modulation side peaks. This allows engineers to verify that their dwdm channels are operating at the correct power and wavelength, and ensure that they will continue to operate properly over time.
The osa also comes in several different sizes, including portable compact units that can be carried in a pocket. These units offer a number of features that allow users to perform a range of dwdm measurements, such as channel wavelength and power tests, drift measurements, and more.
DWDM Measurement
DWDM measurement involves osa dwdm measuring three crucial parameters: power, central wavelength and optical signal-to-noise ratio (OSNR). A portable instrument, such as an optical spectrum analyzer or OSA, is the best choice for testing dense wavelength-division multiplexing systems.
A common type of OSA uses a diffraction grating, which breaks light signals into constituent wavelengths and measures their power. The instrument also contains a detector that receives the reflected signal. Depending on how well the grating works, the unit can offer resolution down to a few thousandths of a nanometer, which is important for DWDM applications.
Other types of diffraction-grating-based OSAs use tunable filters to achieve similar results. However, these instruments are limited by their cost and capability.
Another option is the high-resolution complex OSA, which combines the capabilities of a diffraction grating and a tunable filter. This type of instrument can provide resolution of up to 0.08 pm at 1550 nm and an extended dynamic range of 80 dB, which is important for 40G/100G networks.
For accurate DWDM measurements, an osa should have a good optical rejection ratio (orr). This parameter is the amount of inter-channel noise that the instrument can distinguish from the strong channel. This is especially important when measuring a high-power channel.
The osa should also be able to distinguish different channels at a close distance from each other. This is especially important when testing a high-power DWDM system, because a very strong signal could overlap its weak neighbors and smother them.
A very good osa should also have a large ORR at 50 GHz from the peak, says Moench of JDSU. This will give the osa a clean picture of the spectrum and help it determine the noise floor at a specific distance.
Moreover, a high ORR means that the osa can detect and measure interference from other optical signals in the same spectrum. Consequently, the osa will be able to separate channels and measure inter-channel noise accurately.
A high ORR and a low RBW will also enable osas to detect and measure a wide range of other wavelengths in addition to the traditional telecom bands. This will be useful for a variety of applications, including gas sensing, cell florescence, laser metrology, and more.
DWDM Analysis
The osa dwdm is an optical spectrum analyzer that quantifies and displays the power of an optical light source over a given wavelength range. It is a technology that has been around for some time, but only recently has it become affordable for the mass market.
The best OSAs in the world will offer a wide variety of options and features, all designed to help you get the most out of your network. This includes a full suite of WDM channels including superchannels, flexgrid channel spacing and in-band signal analysis to lower your DWDM installation and maintenance costs.
A good OSA will also deliver the requisite data points to allow for a more thorough spectral analysis. This may include the optical signal-to-noise ratio (OSNR), or power spectral density. It will also help you make smarter decisions about DWDM system design, power balancing and installation, and the likes.
One important feature is resolution bandwidth, or RBW for short. A high RBW OSA will be able to separate the signals with a greater accuracy, which is a key benefit when you’re looking for the best in class spectral quality.
The best RBW OSAs will also have the highest power and wavelength performance for your application needs. They osa dwdm are equipped with a sophisticated algorithm that allows you to calculate the correct signal type and channel configuration for each individual wavelength. This is an essential feature for DWDM systems, where there are multiple wavelengths that need to be combined to achieve maximum signal efficiency.
DWDM Comparison
OSA DWDM Comparison
An optical spectrum analyzer (OSA) is an excellent complementary instrument for the complete characterization of a DWDM system. It offers a number of advantages over a traditional spectrometer including faster scan times and the ability to view detailed spectral information.
The most important feature of an OSA is the ability to measure wavelength, channel power and optical signal noise ratio (OSNR) in an accurate manner. Several factors determine the accuracy of these measurements, including: resolution bandwidth (RBW), wavelength sensitivity and amplitude, the linewidth of the optical signal, and the level of optical noise.
OSAs are typically based on gratings, which reflect light from a beam. Depending on the type of grating, OSAs can have an RBW from 5 pm to 0.1 nm and an ORR of up to 50 dB at 0.2 nm. This means that OSAs can accurately resolve the spectral details of a DWDM system, such as separating close channels.
However, a grating-based OSA is not always appropriate for field testing. Some grating-based OSAs can be too sensitive to polarization. Therefore, an EDFA gain tilt measurement must be performed on the OSA as well to ensure that levels are not affected by polarization.
Some OSAs are based on a double-pass grating, which sends light back to the grating twice before it enters the detector. This design has the advantage of a higher ORR and a wider spectral range than most high-resolution OSAs.
In addition to a more sophisticated design, a grating-based OSA also offers a smaller RBW than a high-resolution OSA. This is essential when analyzing DWDM systems, where wavelengths must be separated by narrower passbands than in lab units.
Another advantage of grating-based OSAs is their wide spectral range, which allows them to analyze superchannels and flexgrids. They are also more durable than other types of OSAs and are suitable for testing a wider range of network technologies, including CWDM.
Other important features include the ability to display information in a variety of formats, such as graphical and tabular displays. The display can also be optimized during or after the test to show only what is needed. For example, a level threshold can be set to only display channels that exceed a specific limit or it can be used to reduce the overall number of channels shown.