Archived — Test Equipment

Most semiconductor lasers have cleaved facets that form the optical cavity. The facets are perpendicular to the surface of the wafer and light is emitted parallel to the surface of the wafer. But for many applications requiring a two-dimensional laser array or monolithic integration of lasers with electronic components, e.g., optical interconnects, it is desirable to have the laser output normal to the surface of the wafer. Such lasers are known as surface emitting lasers (SEL). A class of surface emitting lasers also has an optical cavity normal to the surface of the wafer. These devices are known as vertical-cavity

In many cases, it is not sufficient to eliminate the PDL influence from the insertion-loss result. Instead, the PDL is considered as a separate characteristic and must be measured in addition to the insertion loss. The two most important PDL-measurement techniques are polarization scanning and the Mueller method. Both methods are explained in detail below.   >> Polarization Scanning Method The figure below shows the principle measurement setup for polarization scanning. This measurement is usually based on the fact that laser sources produce nearly 100% polarized light. The polarization controller has to convert the fixed input polarization state to all

>> The Optical Time Domain Reflectometer (OTDR) OTDR is connected to one end of any fiber optic system up to 250km in length. Within a few seconds, we are able to measure the overall loss, or the loss of any part of a system, the overall length of the fiber and the distance between any points of interest. OTDR is a amazing test instrument for fiber optic systems. 1. A Use for Rayleigh Scatter As light travels along the fiber, a small proportion of it is lost by Rayleigh scattering. As the light is scattered in all directions, some of

Buy Fiber Optic Light Source from us. Laser Diodes (LD) are very commonly used in fiber optic communication systems and their characteristics are of primary importance. So here we give a summary of LD’s characteristics. Laser Diode Threshold The above figure shows a laser diode’s output optical power versus injected electrical current  – P/I Curve. As we can see, the output optical power varies as a function of the current passing through the diode. When biased below a threshold current Ith, the output power is very low. But as the current increases over the threshold Ith, the output optical power

:: BER (Bit Error Ratio) Is a Signal Quality Quantitative Measurement of Digital Communication Systems Transmission quality of telecommunication systems can be assessed directly by measuring how well the output signal reproduces the input. Bit Error Ratio (or Rate) is the signal quality concept used for digital communication systems (Signal-to-Noise Ratio SNR is used for analog communication systems instead). BER measurements compare digital input and output signals to assess what fraction of the bits are received incorrectly. It is defined as where is the number of bits received in error over time t, and is the total number of bits