Abstract
This article proposes an optical parametric amplifier (OPA), as an inline-repeater, using a periodically-poled-LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (PPLN) waveguide with over-10-THz amplification bandwidth, and also presents wide-band wavelength-division-multiplexing (WDM) inline-amplified transmission with the OPA. Our PPLN-based OPA is polarization-independent and has a spectrally efficient configuration by filtering phase-conjugated signals (idlers). We implemented our PPLN-based OPA with half its ideal configuration with an over-10-THz amplification bandwidth because of the limited number of PPLN waveguides. The implemented OPA had 5.125-THz amplification bandwidth, gain of beyond 15 dB, and noise figure of less than 5.1-dB. The gain excludes the 5.6-dB loss of an idler rejection filter employed in the transmission experiment so that the implemented OPA can compensate 9.5-dB link loss of transmission fibers and optical components. A 3 × 30.8-km inline-amplified transmission with 41-channel 800-Gbps WDM signal in 125-GHz spacing was successfully demonstrated using our PPLN-based OPA as an inline-repeater. The results also indicate that the OPA's amplification bandwidth can potentially be extended to 10.25 THz.
Highlights
T O INCREASE the capacity of optical communication systems, extending the available optical bandwidth and Manuscript received July 15, 2020; revised October 19, 2020; accepted November 16, 2020
The results indicate that our optical parametric amplifier (OPA) can be applied as an in-line amplifier placed at optical nodes in flexible optical networks as well as increase the available optical bandwidth
The duration between measurements was about 2 seconds. This confirms that normalized generalized mutual information (NGMI) fluctuations are sufficiently small, the result includes all fluctuations due to the transmission system and that the worst channel never falls below the NGMI threshold. These results indicate that 5.125-THz inline-amplified transmission with our PPLN-based OPA can be achieved, and amplification bandwidth can be potentially extended to 10.25 THz by measuring the signal quality of both signals and idlers
Summary
T O INCREASE the capacity of optical communication systems, extending the available optical bandwidth and Manuscript received July 15, 2020; revised October 19, 2020; accepted November 16, 2020. Amplification in an HNLF-based optical parametric amplifier (OPA) is caused by four-wave mixing (FWM) via the third-order nonlinearity of optical fibers, whereas amplification in a PPLN-based OPA is based on quasi-phase-matched (QPM) difference-frequency generation (DFG) due to the second-order nonlinearity of PPLN waveguides. They are based on different phenomena but provide the same functionality. A PPLN-based OPA is expected to achieve low-crosstalk and wide-band amplification for a WDM signal because it is based on second-order nonlinearity, and we can use a configuration in which the high-power pump-light is not located at the signal wavelength band [20]. A re-circulating transmission repeating three 30.8km spans confirmed that a PPLN-based OPA as an inlineamplifier can potentially extend the amplification bandwidth to over 10 THz
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