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Series F Amplified Differential Optical Receivers
with sensitivities to over a million V/W and speeds to 10 GHz
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Updated: March 2010 M,F&A's continuously improved Amplified Differential Optical Receivers allow detection of the difference between two optical signals at bandwidths up to 10 GHz and overall optical conversion gains of 15,000 volts/watt or more. They are perfectly suited for detection of the phase difference between two otherwise identical signals such as in range finding or in phase encoded communication protocols. Other applications include the detection of small optical modulations on a high power or unpredictably variable background. In these modules the background cancellation is done at the optical input stage before amplification, avoiding limitations due to amplifier saturation by the background signal. These modules are available with the same broad range of photodiode and amplifier choices as our Award Winning Series 99 Photodetector Modules. The fully enclosed and potted modules may be used free-standing or mounted to a PC board. Fiber type, connector types, photodiode spectral range, and amplifier may be chosen from our list of standard options or specified by the customer. The result is a Differential Optical Receiver optimized for your particular application. Optical Fiber and ConnectorWe will build your modules with whatever optical fiber, cable and connectors you specify. We stock single-mode 9/125microm and both 50/125microm and 62.5/125microm multimode fiber with 0.9mm polymer buffer and 3mm Kevlar jacket. Other types such as 100/140microm are available. Jacketing options include 0.9mm polymer buffer only or the usual 3mm Kevlar and polymer jacket. All fiber to photodiode connections are angle polished for low (-45dB) back reflection. The input end of the optical fibers will be fitted with whatever optical fiber connections you desire. The range of normal options include: none, i.e. abare fiber pigtail, 2.5mm ceramic ferrule only, NTT-Fc, SC, St, and SMA. The fiber end itself will be polished to any of the standard specifications: Flat, PC, SPC, or APC(8 degrees). If you need something else, just specify so. Optional Light Collecting OpticsIf the signal you want to analyze is in the form of a beam in free-space we can provide light collecting optics instead of or in addition to the optical fiber connectors described above. The simplest is a 2mm diameter GRIN lens and ferrule assembly permanently fixed on the end of the fiber. For larger beams a 6mm diameter fixed focus aspheric lens assembly is available. We also offer a micro-alignable fixture with 18mm aperture focusable achromatic lens. Precision fine thread adjustments allow you to maximize the coupling of the incoming beam into the fiber. The unit is also directly compatible with "micro-rail" optical component systems made by Newport, Melles-Griot, ThorLabs and others and is "C" threaded for compatibility with Edmund Scientific's modular component line. Finally, large aperture catadioptric systems for collecting light from weak, distended or distant sources can be provided. Details available upon inquiry. Photodiode Selection
The two major considerations in selecting the photodiode for your application are spectral response and speed. Photodiodes based on different semiconductor materials have, in general, different ranges of light wavelength to which they are most sensitive. For example, Silicon based diodes are most sensitive in the 400nm (nearly UV) to 1000nm (near IR) spectral range and cover the visible well. InGaAs is relatively insensitive to visible light but responds well to the IR used in information systems. The intrinsic speed of the photodiode is also determined by the semiconductor material. The higher electron mobility in InGaAs allows response times which are simply not attainable with Si. Our latest GaAs model offers unprecedented speed in the visible range. Other factors which might be important to your needs, such as Dark Current and Capacitance are also listed in the table on Photodiode Specifications. The photodiodes in all our receivers are reverse biased to minimize intrinsic capacitance for maximally fast response. Photodiode SpecificationsSpecifications are listed for the usual photodiodes. Others are available, call or write for details.
Transimpedance Amplifier OptionThe amplfiers used in the Series F Differential Optical Receivers are hybrid bipolar high electron mobility technology in Darlington configurations. All amplifier options are available in AC coupled configurations. The Mod1A, 2A, and 4A are multi-staged and are availabe only in AC coupled configurations. The Mod1, 2, and 4 may be ordered in true DC coupled versions.
Transimpedance Amplifier SpecificationsThe amplifier selection for Series F Amplified Differential Optical Receivers are listed below. We have renamed the single stage detectors with a D for DC coupled and an A for AC coupled to simplfy specification and ordering. True DC Coupling - Single Stage
AC Coupling - Single Stage
M,F&A has added greatly increased the amplification available in the AC coupled Photodetector Modules. The new internal multi-stage AC coupled transimpedance amplifiers provide overall conversion gains as high as 60,000 volts/watt in two stages and over a million volts/watt in three stages, allowing detection of sub-microwatt signals.
AC Coupling - Two Stage
AC Coupling - Three Stage
Note: Due to the relatively low output power of the Mod 4 amplifier, those modules with an amplifier Model Number ending in 4 will have Transimpedances about one-half of the value specified above when driving a 50 ohm termination load. For example, the Mod 44A delivers approximately 60,000 volts/amp into a high impedance termination and about 30,000 volts/amp into 50 ohms. For all other models the specified values are valid for either Hi-Z or 50 ohm termination. This technology is developing rapidly. Other options are available. If your needs are not met by the choices lisetd, please contact us with your requirements or specifications.
Estimation of Signal LevelYou can estimate the signal level (voltage) that you can expect to see, for your light intensity, directly from the of the photodiode and the Transimpedance of the amplifier, from the following relation: Signal [volts] = (I1 - I2) [watts] • Responsivity [amps/watt] • Transimpedance [ohms] where I1 and I2 are the light power levels of the two input signals. Noise SpecificationsMeasurements of the noise spectrum have been made by independent labs on several of our systems. In all measurements the results were consistent with or better than the specifications shown. The noise from the photodiodes themselves is several orders of magnitude below that of the amplifiers and may be ignored. In general, we have found that the noise contributed by our amplified photodiode systems is below or comparable to the intrinsic noise floor (about 1mV RMS) of most high speed oscilloscopes and digital data acquisition systems.
Output Electrical ConnectorThe standard output electronic connector is SMA male. If you need something different, just specify on the Order Form or call to discuss your needs. Internal and Output CouplingThe Mod 1A, 2A and 4A amplifiers are several stage systems which are capacitively coupled. The photodiode input and the output signal in modules using these amplifiers are also AC coupled through capacitors, normally 0.1 microF. The low frequency cutoff (-3dB) is about 30 KHz. Higher cutoff frequency may be requested on the order form. Receivers using the Mod 1, 2 or 4 amplifiers may be ordered in a true DC coupled version. PackagingThese Receivers are normally packaged in a solid metal RF enclosure. Dimensions are approximately 1.5" square by 0.75" exclusive of connectors and cables. The free-standing version has an integral shielded power cable. the PC mountable version has solder lugs for the power connections as shown in the photo. We will attempt to meet any special packaging or environmental requirements. Output Electrical ConnectorElectronic output connectors are SMA in either gender. If you need something other than SMA, specify on the Order Form or call to discuss your needs. Power ConsiderationsAny power supply is a potential source of noise. The M, F & A External Power Supply provides noise free power to the photodiode and amplifiers from gel-cell batteries which are charged when the differential optical receiver is not in use. When the differential optical receiver is active, the system is completely disconnected from the external AC source, and power is provided through a shielded cable with a connector that mates the module to the power supply. A multiple receiver version with individual control over each is available.
Series F Amplified Differential Optical Receivers Summary and Prices
Please note that these modules contain technology at the leading edge of the state of the art. How to OrderWe will build your Differential Optical Receiver to your specifications. The price of your detector is simply the addition of the prices of specified options with cost amounts listed. Email us your specifications from the list under Summary and Prices above. We will return a formal quotation to confirm your specifications and expected delivery time. Quantity discounts are available, send a Request for Quotation.
email: sales@mfaoptics.com |
