Adtran Gmbh

John Gordon Brooks

Leif J Sandstrom

Daniel M Joffe

Michael D Turner

Kevin W Schneider

George Elliott Bekken

A laser tuning system includes an optical transmitter having a tunable laser that transmits optical signals at various wavelengths to an optical fiber through an optical component, which attenuates a range of wavelengths of the optical signal. An optical detector detects optical returns that have been reflected from the fiber at points beyond the optical component. A tuning control module analyzes the optical returns in order to provide a tuning value for tuning the laser to a desired wavelength. As an example, the laser may be tuned in order to maximize or otherwise increase the amount of optical power passing through the optical component.

Systems and methods for tuning lasers using reflected optical signals

An optical transmission system transmits an optical signal over an optical path. Reflections of the optical signal are received at an optical detector which generates an analog reflection signal. The analog reflection signal includes both a desired portion and an undesired portion. Correlators of an OTDR system generate correlation values based on the analog reflection signal. A subset of the correlation values are associated with locations of the optical path that cause the reflections that result in the undesired portion of the reflected signal. A filter uses these correlation values to generate a cancellation signal that is subtracted from the analog reflection signal, reducing the undesired portion of the signal that must be processed.

Systems and methods for cancellation of undesired reflections in testing of optical fibers

Methods, systems, and apparatus for automatically identifying rogue Optical Network Unit (ONU) are disclosed. In one aspect, an Optical Line Terminal (OLT) determines dark power on a fiber optic link over a period of time. For a given ONU, the OLT determines an optical power of high signals and an optical power of low signals received over the fiber optic link during a timeslot assigned to the given ONU, determines a modified optical power of the high signals and a modified optical power of the low signals based on differences between the optical power of the respective signals and the dark power, determines an extinction ratio based on a ratio of the modified optical power of the high signals relative to the modified optical power of the low signals, and identifies the given ONU as a rogue ONU when the extinction ratio is outside of a specified range.

Automatic rogue ONU detection

A correlation optical time domain reflectometer (OTDR) system embeds an OTDR signal in a digital data signal that is to be converted into an optical signal and transmitted across an optical fiber to a remote receiver. In particular, the digital data signal is amplitude modulated with the OTDR signal, which is based on a pseudo noise (PN) sequence, such as an M-sequence. The amplitude modulation is relatively small, for example, less than about 10% of the digital data signal's peak amplitude in an effort to limit the OTDR signal's effect on communication performance. A sequence recovery element receives reflections from the optical fiber and converts the reflections to digital samples. Each digital sample from the sequence recovery element is correlated by correlators that respectively correspond to delays and, hence, locations along the optical fiber, and accumulators accumulate the correlation values from the correlators. Based on the accumulated values, the correlation OTDR system unobtrusively identifies anomaly locations along the optical fiber while payload data is being communicated across the fiber.

Systems and methods for unobtrusively testing optical fibers

A correlation system, such as a correlation optical time domain reflectometer (OTDR) system, transmits a correlation sequence, such as an M-sequence, and measures the returns of the correlation sequence over time. The system correlates the transmitted sequence with the returns to provide correlation measurement values that respectively correspond to different distances from the point of transmission. A correlation error compensation element adjusts each correlation measurement value in order to cancel the contribution of the correlation error floor from the measurements to provide compensated measurement values that are substantially free of the effects of the correlation error floor.

Correlation systems and methods with error compensation

The present disclosure generally pertains to systems and methods for cancelling crosstalk. A multiple input, multiple output (MIMO) system in accordance with one exemplary embodiment of the present disclosure has a plurality of receivers, which are capable of exchanging information with one another. Each receiver is coupled to a respective subscriber line and receives signals from a remote transmitter. In each path of the MIMO system, in domain crosstalk and possibly some combination of noise, alien crosstalk, and/or other interference such as RF interference, is canceled from the signal being processed. In some cases, a cancellation signal for cancelling crosstalk is based on an output of a symbol decision element, such as a slicer or decoder, thereby improving the accuracy of the cancellation signal.

Growing community of inventors

Madison, AL, United States of America

John Gordon Brooks