Reaching for 110 GHz – Industry First for Both Optical Receiver and Transmitter Test
2019-10-22 | 3 min read
At higher baud rates of 100 GBaud and beyond in NRZ, PAM and coherent formats, high-bandwidth S-parameter testing for magnitude and phase becomes extremely important.
Until now, in the industry full S-Parameter measurement up to 110 GHz bandwidth only was available for optical transmitters. The new N4372E lightwave component analyzer (LCA) now adds opto-electronic S-parameter testing for optical receivers up to 110GHz, and within an extended wavelength range from 1620 nm down to 1260 nm, thanks to a high bandwidth transmitter that is calibrated traceable to the National Institute of Standards and Technology (NIST).
Target Test Devices
Transmitters and receivers are typically tested for their frequency response in both magnitude and phase and for electrical return loss over a range of bias voltages, optical input power levels, operating currents and ambient temperatures. The LCA’s built-in optical power meter allows to measure the transmitter DUT optical output power and to check and control the user-selectable operating power for receiver test, but also gives an indication of a bent fiber or a bad connection. The LCA optical transmitter’s input port is normally connected to the built-in laser source of the LCA controller. With an auxiliary tunable laser, the test of receiver S-parameters over wavelength is enabled. With the LCA’s fast update of the electro-optic and electric S-parameter measurement, operating parameters quickly be adjusted to determine the optimum operating point of such devices.
PIN photodiodes, avalanche photodiodes (APD), receiver optical subassemblies (ROSA) and integrated PIN-TIA receivers are examples of optical receivers. 4-port PNA versions of the LCA can characterize PIN-TIA combinations with differential output for differential gain, common-mode rejection and gain imbalance, using three RF extender heads.
Figure 1: Photodiode test configuration
Mach-Zehnder modulators (MZM), electro-absorption modulators (EAM), directly modulated lasers and transmitter optical subassemblies (TOSA) represent the most common optical transmitters. Dual-drive optical modulators can be characterized with 4-port PNA versions of the LCA, using three RF extender heads.
Figure 2: Optical transmitter test configuration