Hello, everyone!
Today, I would like to share with you an
article about Transmission over Graded-Index Plastic Optical Fiber.
Here, we will demonstrate that GI-POF can transmit 40Gb/s signal with a BER smaller than 2x10-3.
The experimental configuration is shown schematically in Figure 1. The CML transmitter setup, including the driving voltage of the laser, and the OSR filter is kept similar as these in the below Figure.
Figure. (a) Waveform and flat-topped chirp and (b) eye diagrams in different distance for 40-Gb/s signals.
The optical spectra with 0.01-nm resolution before and after OSR filter are shown in Figure 1 insets (a) and (b). After the OSR filter and EDFA, the CML signal is launched into 100-m commercially available GI-POF (GigaPOF-50SR, Thorlabs) for transmission.
Figure 1. Schematic of experimental setup for the chirp-managed signal transmission over 100 m GI-POF at 42.8 Gb/s. Inset: received optical spectrum (0.01 nm).
(a): Before OSR filter; (b): After OSR filter; (c): After 100m GI-POF.
Due to the lack of a photodiode with multi-mode input and a bandwidth up to 40 GHs, we use a regular photodiode with single-mode input and bandwidth of 45 GHs. Therefore, there is additional insertion loss when we connect the GI-POF with the SMF-28. The coupler loss from GI-POF to SMF-28 is approximately 10 dB.
The signal power launched into GI- POF is 23 dBm, and the output power after the 100-m GI-POF is -4 dBm. The insertion loss is over 27 dB, however, the insertion loss at this wavelength can be largely reduced when the laser is operated at 1310 nm or 850 nm. After coupling with the SMF-28, the optical power is -14 dBm.
The receiver consists of an EDFA preamplifier and a 45 GHs high-speed single-mode coupled photodiode. The received optical spectrum after preamplifier is shown in Figure 1 inset (c). Another TOF with 3-dB bandwidth of 1 nm is used to reduce ASE noise from the EDFA.
A commercial error analyser is used to measure BER performance while the clock signals for the error analyser are directly obtained from the pattern generator. We evaluate the optical signal-to-noise ratio (OSNR) requirement for this CML laser at 42.8- Gb/s as shown in Figure 1. The measurement results show that the required OSNR for the 42.8-Gb/s CML signal is 24.8 dB (0.1 nm) when the BER equals to 2╳ 10-3.
Figure 2. Measured BER as a function of OSNR for the CML signal at 42.8 Gb/s before transmission.
Figure 2 shows the measured BER performance and the corresponding eye diagrams after 100-m GI-POF transmission at different bit rates, including 34, 36, 40 and 42.8 Gb/s. For the CML signal before transmission, the lowest BERs are 3╳ 10-6 and 1╳ 10-7 at the bit rate of 42.8 and 40-Gb/s, respectively.
After transmission over 100-m GI-POF, the BER value is raised from 1.0╳ 10-9 to 3.6╳ 10-4 while the bit rate increased from 34 Gb/s to 42.8 Gb/s. Even if the bit rate is 42.8 Gb/s, error-free transmission can be realised at the BER of 3.6╳ 10-4 using FEC modules.
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