Optical Spectrum Analyzer Application Notes

Ultra High Resolution OSA for Characterizing and interrogating Fiber Bragg Grating Sensors

The APEX Technologies Ultra High Resolution Optical Spectrum Analyzer (OSA) can be used to measure the active/passive optical component insertion loss/gain thanks to the possibility to synchronize the internal Tunable Laser Source and the OSA sweepings. In this context, the APEX OSA remains a perfect tool to measure the Fiber Bragg Grating (FBG) Sensor reflection with 1 MHz of resolution, 63 dB dynamic and 0.3 pm wavelength relative accuracy.

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FBG sensors polarization-dependent reflection measured by APEX Technologies OSA

Ultra High Resolution OSA: a perfect tool for optical Orthogonal Frequency Division Multiplexing (OFDM) measurement and adjustment

This paper shows the strong contribution of the High Resolution Optical Spectrum Analyzer not only in measuring optical Orthogonal Frequency Division Multiplexing (OFDM) signals but also in adapting them to any other modulation techniques. In fact, we show the ability of the High Resolution Optical Spectrum Analyzer to verify the OFDM signal compatibility with the Single Side-Band (SSB) modulation technique when adjusting the operating point of the SSB signal generator. We demontrate the utility of High Resolution Optical Spectrum Analyzer in adjusting the optimal operating point of the complex Mach Zehnder Modulator used for the coherent dual polarization multi-band OFDM generation.

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SSB-OFDM spectrum with 40MHz MHz sub-carriers spacing measured by the APEX Technologies High Resolution Optical Spectrum Analyzer
SSB-OFDM spectrum with 40MHz MHz sub-carriers spacing measured by the APEX Technologies High Resolution Optical Spectrum Analyzer

 

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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Spectral measurement of a Comb with 20 MHz repetition frequency made by the APEX Technologies High Resolution Optical Spectrum Analyzer
Spectral measurement of a Comb with 20 MHz repetition frequency made by the APEX Technologies High Resolution Optical Spectrum Analyzer

 

High Resolution Optical Spectrum Analyzer used for Experimental demonstration of 23.6-Gb/s OFDM with a colorless transmitter

This paper shows the great utility of our High Resolution Optical Spectrum Analyzer AP2040/AP2050 series in demonstrating a 23.6-Gb/s optical Orthogonal Freqency Division Multiplexing (OFDM) (20-Gb/s after coding) with a colorless transmitter, realized by optical IQ multiplexing. In combination with 8-QAM coding, DACs with only 4-GHz bandwidth are required to generate the 23.6-Gb/s signal.

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Optical Spectrum of the 23.6-Gb/s OFDM signal measured with APEX Technologies High resolution Optical Spectrum Analyzer
Optical Spectrum of the 23.6-Gb/s OFDM signal measured with APEX Technologies High resolution Optical Spectrum Analyzer

 

Gain Measurements of Fabry-Pérot InP/InGaAsP Lasers using an Ultra High Resolution Optical Spectrum Analyzer

This application note presents the time measurements of the optical gain in a semiconductor laser using our High Resolution Optical Spectrum Analyzer AP2040/AP2050 series. The high resolution allows for accurate gain measurements close to the lasing threshold. This is demonstrated by gain measurements on a bulk InGaAsP 1.5 μm Fabry-Perot laser. Combined with direct measurement of transparency carrier density values, parameters were determined for characterizing the gain at a range of wavelengths and temperatures. The necessity of the use of a logarithmic gain model is shown.

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Typical example of a recorded subthreshold spectrum of a Fabry-Perot laser made with APEX Technologies ultra high resolution Optical Spectrum Analyzer.
Typical example of a recorded subthreshold spectrum of a Fabry-Perot laser made with APEX Technologies ultra high resolution Optical Spectrum Analyzer.

 

Ultra High Resolution Optical Spectrum Analyzer used for Generation of Coherent Multi-Carrier Signals by Gain Switching of Discrete Mode Lasers

This paper shows the utility of our High Resolution Optical Spectrum Analyzer AP2040/AP2050 series in the generation of a highly coherent multi-carrier signals. It consists on eight clearly resolved 10.7GHz coherent sidebands generated within 3dB of the spectral envelope peak and with an extinction ratio in excess of 45dB, by gain switching a discrete mode (DM) laser.

Thanks to the High Resolution Optical Spectrum Analyzer, we can analyse the generated spectral comb corresponding picosecond pulse train at a repetition rate of 10.7GHz with a pulse duration of 24ps and a temporal jitter of 450fs.

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Expanded frequency optical comb spectrum measured by APEX Technologies High Resolution Optical Spectrum Analyzer
Expanded frequency optical comb spectrum measured by APEX Technologies High Resolution Optical Spectrum Analyzer

 

64-QAM-encoded Optical OFDM signal spectrum measurement using High Resolution Optical Spectrum Analyzers

This paper shows the contribution of our High Resolution Optical Spectrum Anlyzer in evaluating  low-cost, un-cooled vertical cavity surface-emitting lasers (VCSELs) as intensity modulators in real-time optical OFDM (OOFDM) transceivers.  64-QAM-encoded OOFDM signal spectra at the output of the VCSEL intensity modulator with equal power loading and adaptive power loading are compared using High Resolution Optical Spectrum Analyzers AP2040/AP2050 series. End-to-end real-time transmission of 11.25Gb/s 64-QAM-encoded OOFDM signals over simple intensity modulation and direct detection, 25km SSMF PON systems is experimentally demonstrated with a power penalty of 0.5dB. The low extinction ratio of the VCSEL intensity-modulated OOFDM signal is identified to be the dominant factor determining the maximum obtainable transmission performance. This work is of great value as it demonstrates the possibility of future mass production of cost-effective OOFDM transceivers for PON applications.

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64QAM-OFDM
Real-time 64-QAM-encoded OOFDM signal spectra at the output of the VCSEL intensity modulator with equal power loading and adaptive power loading using High Resolution Optical Spectrum Analyzer.

 

Ultra High Resolution Optical Spectrum Analyzer used for the generation of coherent Dual-Polarization Multi-Band OFDM signals

The Ultra High Resolution Optical Spectrum Analyzer is a high efficient tool for generating and adjusting coherent Dual-Polarization Multi-Band Orthogonal Frequency Division Multiplexing (DP-MB-OFDM) signals. This paper shows an experimental comparison of the DP-MB-OFDM signals and Quadrature Phase Shift Keying QPSK for 100 Gbps long-haul transport over legacy infrastructure combining G.652 fiber and 10 Gbps WDM system. We show that DP-MB-OFDM and DP-QPSK have nearly the same performance at 100 Gbps after transmission over a 10×100 km fiber line.

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100Gbs-DP-MB-OFDM
Optical spectrum of a 100 Gbps DP-MB-OFDM measured by the High Resolution Optical Spectrum Analyzer