Optical Complex Spectrum Analyzer Application Notes

Optical Complex Spectrum Analyzer principle

This paper explains clearly the patented method used by the Apex Technologies Optical Complex Spectrum Analyzer AP2441B/AP2443B developed in collaboration with France Telecom scientists. It is based upon a spectral analysis of the optical field; it extracts the amplitude and the phase of each frequency component (whereas classic optical spectrum analyzers measure only the power spectral density, giving only the amplitude). By knowing the amplitude and the phase of each spectral component, the temporal variations of the amplitude and the phase can be calculated by means of the Fourier transform, providing the intensity, the chirp and the optical phase as a function of time.

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optical-complex-spectrum-anlyzer-principle

optical-complex-spectrum-anlyzer-principle

 

80Gb/s Multi-Level BPSK experiment with an InPMonolithic Source Based on Prefixed Optical Phase Switching

Improved-speed full-monolithic BPSK transmitter based on prefixed phase switching by fast Electro-Absorption Modulators has been realized on InP using a Selective Area Growth integrating circuit technology. It has been used in 80Gb/s multi-level BPSK format modulation experiments. Simplicity, speed scalability, ultra-small footprint and low power drive of the monolithic circuit are attractive for advanced format migration towards low-cost applications.

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Multi-level BPSK phase and power sequence (upper), constellation with transitions and tributary eye (lower) of the generated 80Gb/s signal

Multi-level BPSK phase and power sequence (upper), constellation with transitions and tributary eye (lower) of the generated 80Gb/s signal

 

 

Ultra High Resolution Optical Spectrum Analyzer/Optical Complex Spectrum Analyzer for Characterizing and Evaluating Optical Frequency Comb Sources

This paper is devoted to present the capacity of the High Resolution Optical Spectrum Analyzer/Optical Complex Spectrum Analyzer to show clearly all the Optical Comb sidebands even with a few tens of MHz spacing. Two commercial Optical Frequency Comb Sources (OFCS) are evaluated by the equipment in order to verify the main specifications mentioned in OFCS datasheets and to adjust the operating point. We depict the strong contribution of the High Resolution Optical Spectrum Analyzer/Optical Complex Spectrum Analyzer in the implementation of new OFCS’s architectures marked by the testimony of one of our customers.

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comb-pulse-and-chirp-measurement

comb-pulse-and-chirp-measurement

 

Optical Complex Spectrum Analyzer AP2441B/AP2443B : High efficient tool for any kind of usual modulation format measurements

This application note proves the high efficiency of the Optical Complex Spectrum Analyzer AP2441B/AP2443B in measuring and testing any kind of usual modulation formats. Compared to a standard oscilloscope, the Optical Complex Spectrum Analyzer AP2441B/AP2443B has a maximum bandwidth > 6 THz due the complex spectral analysis principle giving access to the optical phase and intensity both in frequency and time domains. Therefore, the Optical Complex Spectrum Analyzer has no baud/bit rate limitations. Examples of RZ short pulses (2 ps pulse-width), pulse time resolved chirp, Differential Phase-Shift Keying (DPSK) modulation and Quadrature Phase-Shift Keying (QPSK) modulation measurements are presented.

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40gbs-qpsk-modulation

40gbs-qpsk-modulation

 

Optical intensity and chirp measurement of a Mach-Zehnder Electro-optic travelling wave modulators with Optical Complex Spectrum Analyzer

The discussion exposed in this paper is based on a synthesis of several elements collected in some publications dealing with fundamental characteristics of Mach-Zehnder electro-optic traveling wave intensity modulators. We draw an analysis of the optical response of these modulators to a time varying drive voltage, modelized after a description of their technological conception. Then we review the important parameters to study for the use of these modulators in optical transmissions (optical response bandwidth, chirp parameter). We present the properties of these parameters with respect to the previous analysis, and we show that they can be characterized independently using the Optical Complex Spectrum Analyzer AP2441B/AP2443B, which is of great importance to analyse the performances of such modulators in long haul transmissions.

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instensity-and-chirp-temporal-parameters-of-a-MZI-modulator

instensity-and-chirp-temporal-parameters-of-a-MZI-modulator

 

Effects of chirp induction mechanism on spectral broadening in LiNbO3 modulators using Optical Complex Spectrum Analyzer

The spectrum of a chirped optical NRZ data stream obtained by an external Mach-Zehnder Modulator (MZM) is analyzed using the Optical Complex Spectrum Analyzer AP2441B/AP2443B. We  demonstrate that it is possible to induce chirp without broadening the optical spectrum by employing a MZM with optical power unbalancing in the two waveguides. For standard chirped MZM (different electrical field on the two arms), such as z-cut LiNbO3 modulators, the broadening as a function of chirp.

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mzi-time-resolved-chirp-and-inetensity-measurement

mzi-time-resolved-chirp-and-inetensity-measurement

 

Differential Quadrature Phase Shift Keying (DQPSK) modulation characteristics using Optical Complex Spectrum Analyzer

This paper depicts the strong contribution of the Optical Complex Spectrum Analyzer AP2441B/AP2443B in characterizing and evaluating 43 Gb/s DQPSK (Differential Quadrature Shift Keying) modulators thanks to its ability to display the phase eye pattern and the constellation. Low-drive-voltage (3.5 V) and uniform modulation characteristics of MZIs (Mach Zehnder Modulators) were achieved with Z-cut dual-drive nested-MZIs structure and the wide-gap design between signal and ground electrodes, resulting in precise constellation mappings in 43 Gb/s DQPSK modulation.

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constellation-and-eye-diagram-qpsk

constellation-and-eye-diagram-qpsk

 

Chromatic dispersion measurement with Optical Complex Spectrum Analyzer

Based on complex spectral analysis of the optical field, the Optical Complex Spectrum Analyzer AP2441B/AP2443B is able to measure the chromatic dispersion and the group delay of a transmission line. This paper is dedicated to explain clearly the measurement method of two examples of a 13.2 km standard Single Mode Fiber (SMF) length using a 10 Gb/s modulated signal produced by a Mach Zehnder modulator and a 12.4 km SMF using an optical frequency comb generator. Optional software (OCSA04-Group delay and chromatic dispersion analysis) can be integrated in the equipment in order to display the group delay and the chromatic dispersion as function of the wavelength/frequency. For accuracy issues, the paper presents a solution by using averaging functions.

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chromatic-dispersion

chromatic-dispersion