Fiber optic micro-doppler ladar system and operating method therefor

A micro-doppler ladar system for identifying and analyzing a target of interest, comprising:

• first means for generating a primary laser beam;
• second means for amplifying said primary laser beam in an optical fiber amplifier means so as to generate a transmit laser beam;
• third means for transmitting said transmit laser beam towards the target of interest;
• fourth means for receiving backscattered light produced by interaction between said transmit laser beam and the target of interest and for generating an electrical signal indicative of the target of interest;
• fifth means for determining range and velocity responsive to said electrical signal;
• and
• sixth means for determining a characteristic signature of the target of interest different from both range and velocity.

A method of operating a micro-doppler ladar system including a transmitter and coherent receiver for identifying and analyzing a target of interest, the method comprising the steps of:

• generating a primary laser beam;
• amplifying said primary laser beam in an optical fiber amplifier so as to generate a transmit laser beam;
• transmitting said transmit laser beam towards the target of interest;
• receiving backscattered light produced by interaction between said transmit laser beam and the target of interest and for generating an electrical signal indicative of the target of interest;
• determining range and velocity responsive to said electrical signal;
• and
• ascertaining a characteristic signature of the target of interest different from both range and velocity.

A transmitter for a micro-doppler ladar system adapted to identify and analyze a target of interest, comprising:

• a master oscillator for generating a primary laser beam;
• a voltage controlled oscillator (VCO) for generating a VCO signal having a predetermined, repetitive frequency pattern;
• a frequency shifting device for varying the frequency of said primary laser beam responsive to said VCO signal to thereby produce a frequency-varying primary laser signal;
• and
• an optical fiber amplifier for amplifying said frequency-varying primary laser signal to thereby produce a transmit laser beams
• wherein said optical fiber amplifier comprises:
• N serially coupled rare earth doped optical fiber sections:
• and
• N pump sources, each of said pump sources operatively connected to a corresponding one of said optical fiber sections,
• wherein N is an integer greater than or equal to 2.

A transmitter for a micro-doppler ladar system adapted to identify and analyze a target of interest, comprising:

• a master oscillator for generating a primary laser beam;
• a voltage controlled oscillator (VCO) for generating a VCO signal having a predetermined, repetitive frequency pattern;
• a frequency shifting device for varying the frequency of said primary laser beam responsive to said VCO signal to thereby produce a frequency-varying primary laser signal;
• and
• an optical fiber amplifier for amplifying said frequency-varying primary laser signal to thereby produce a transmit laser beam,
• wherein said optical fiber amplifier comprises:
• a beam splitter receiving said frequency-varying primary laser beam and generating N secondary laser beams;
• N parallel rare earth doped optical fiber sections, each of said optical fiber sections amplifying a respective one of said N secondary laser beams to thereby produce N tertiary laser beams;
• and
• an optical combiner combining said N tertiary laser beams to thereby produce said transmit laser beam,
• wherein N is an integer greater than or equal to 2.

A micro-doppler ladar system for identifying and analyzing a target of interest, comprising:

• a transmitter for producing a transmit laser beam by amplification of a primary laser beam in an optical fiber amplifier, said amplifier including:
• a master oscillator for generating the primary laser beam;
• a voltage controlled oscillator (VCO) for generating a VCO signal having a predetermined, repetitive frequency pattern;
• a frequency shifting device for varying the frequency of said primary laser beam responsive to said VCO signal to thereby produce a frequency-varying primary laser signal;
• and
• an optical fiber amplifier for amplifying said frequency-varying primary laser signal to thereby produce a transmit laser beam;
• a coherent receiver responsive to backscattered light produced by interaction of said transmit laser beam with the target of interest and generating range and velocity data and a characteristic signature of the target of interest, said coherent receiver including:
• an optical fiber pre-amplifier for amplifying said backscattered light to thereby produce an amplified return laser beam;
• a phase locked loop receiving said primary laser beam and said amplified return laser beam for generating an electrical signal indicative of range, velocity and a characteristic signature of the target of interest;
• and
• a controller for controlling operation of said transmitter and said receiver in a target acquisition mode of operation in which said range and velocity data are easily extracted from said electrical signals and a signature acquisition mode of operation in which said characteristic signature is easily extracted from said electrical signal.