Browsing by Author "Fang, LiMing"

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APD-based Delay-Division-Multiplexing OFDM-PONs
(2018-01-01)
Hsu, Jhih-Hao
;
Yu, Min
;
Chia-Chien
;
Lin, Chi-Hsiang
;
Lin, Chun-Ting
Based on pre-allocated relative sampling delays among optical network users (ONUs) in an orthogonal frequency division multiplexing (OFDM) passive optical network (PON), the delay-division-multiplexing (DDM) technique employs signal pre-processing to enable demand data to be received by sub-Nyquist analog-to-digital sampling. This work employed an avalanche photodiode (APD) in a DDM-OFDM-PON to achieve higher loss budget, compared to a p-i-n photodiode (PIN). To successfully enable the pre-processing, however, the knowledge of channel response is required; thus, it is critical to estimate complete channel response in DDM-OFDM systems under the constraint of sub-Nyquist sampling. To avoid spectral overlapping in channel estimation, the subcarriers of training symbols in different frequency zones are allocated to different time slots. Unfortunately, this scheme may sustain inaccurate channel estimation due to different degrees of APD saturation for training subcarriers at different frequency zones, leading to significant penalty in performance. Thus, careful control of electrical driving power and optical received power for the training symbols will be important to reduce the impact of saturation on channel estimation, thereby improving transmission performance. We experimentally examined the impact of the accuracy of channel estimation in a 25-Gbps APD-based OFDM-PON. Compared to a PIN, we successfully demonstrated the DDM scheme based on an APD and 1/32 of Nyquist rate with 5-dB improvement in sensitivity after 25-km fiber transmission.
Employing Hybrid sub-Nyquist Sampling Rates to Support Heterogeneous Services of Varying Capacity in 25-Gbps DDM-OFDM-PON
(2018-04-01)
Hsu, Jhih-Hao
;
Yu, Min
;
Wei, Chia-Chien
;
Lin, Chi-Hsiang
;
Lin, Chun-Ting
Delay-division-multiplexing (DDM) involves the use of signal preprocessing for the detection of data via sub-Nyquist analog-to-digital sampling, based on preallocated relative sampling delays among optical network users (ONUs) in an orthogonal frequency-division multiplexing (OFDM) passive optical network (PON). If a DDM-PON consists of M virtual groups, the sampling rate at the receivers is only 1/M of the Nyquist rate, but the maximum capacity of each ONU is fixed at 1/M of the total capacity. In this study, we developed a novel DDM scheme that uses hybrid sub-Nyquist sampling rates to accommodate heterogeneous services of different capacities in an OFDM-PON. To equalize the transmission performances using hybrid sub-Nyquist sampling rates, the modification of preprocessing was proposed, and its necessity was demonstrated. Without loss of generality, we experimentally demonstrated a 25-Gbps DDM-OFDM-PON using hybrid sampling at 1/2, 1/8, and 1/32 (or 1/8, 1/16, and 1/32) of the Nyquist rate. Compared to a DDM-PON with a fixed sub-Nyquist rate, the received signals based on hybrid sub-Nyquist sampling rates show similar sensitivities. A loss budget of 26 dB was experimentally achieved using all sub-Nyquist sampling rates after employing the modified preprocessing.
Novel DDM-OFDM-PON with Hybrid Sub-Nyquist Sampling Rates Featuring Heterogeneous ONUs with Different Capacities
(2018-01-01)
Hsu, Jhih-Hao
;
Yu, Min
;
Wei, Chia-Chien
;
Lin, Chi-Hsiang
;
Lin, Chun-Ting
We propose a delay-division-multiplexing-OFDM-PON (DDM-OFDM-PON) with hybrid sub-Nyquist sampling rates, wherein heterogeneous ONUs can request different capacities. 26-dB loss budget in 25-km 25-Gbps DDM-OFDM-PON was achieved using hybrid sampling at 1/32 / 1/16 / 1/8 or 1/32 / 1/8 / 1/2 Nyquist rates.
Novel Time Synchronization Scheme in Delay-Division-Multiplexing OFDM-PON Using Sub-Nyquist Sampling
(2019-01-01)
Yu, Min
;
Liu, Fumin
;
Chen, Wei-Lun
;
Lin, Chun-Ting
;
Zhou, Lei
We propose a novel time synchronization scheme in a DDM-OFDM-PON under the constraint of sub-Nyquist sampling. In a 25-Gb/s DDM-PON, the scheme can acquire precise delays, making the delay-related penalty in SNR <0.2 dB.