Photonic aided vector millimeter-wave signal generation
without digital-to-analog converter
Yanyi Wang (王演祎)
*
, Kaihui Wang (王凯辉), Wen Zhou (周 雯), and Jianjun Yu (余建军)
Shanghai Institute for Advanced Communication and Data Science, Key Laboratory for Information Science of Electromagnetic Waves, Fudan University,
Shanghai 200433, China
*Corresponding author: 19110720079@fudan.edu.cn
Received July 12, 2020 | Accepted September 4, 2020 | Posted Online November 20, 2020
A novel scheme of photonic aided vector millimeter-wave (mm-wave) signal generation without a digital-to-analog con-
verter (DAC) is proposed. Based on our scheme, a 20 Gb/s 4-ary quadrature amplitude modulation (4-QAM) mm-wave signal
is generated without using a DAC. The experiment results demonstrate that the bit error rate (BER) of 20 Gb/s 4-QAM mm-
wave signal can reach below the hard-decision forward-error-correction threshold after a delivery over 1 m wireless dis-
tance. Because the DAC is not required, it can reduce the system cost. Besides, by using photonic technology, the system is
easily integrated to create large-scale production and application in high-speed optical communication.
Keywords: photonic aiding; millimeter-wave; digital-to-analog converter.
DOI: 10.3788/COL202119.011101
1. Introduction
With the advantages of large available bandwidth and small
wireless interference, millimeter-wave (mm-wave) can be widely
used in 5G/6G communication systems
[1–11]
. At present, due to
the bandwidth limitation of the electrical device, it is difficult
to generate 10 GHz or higher mm-wave signal in the electrical
domain. The photonic aided mm-wave generation techniques,
involving remote heterodyning
[12–14]
and external intensity
modulation
[15–20]
, have been expected to solve this problem.
Meanwhile, in order to improve the spectral efficiency and the
transmission rate in mm-wave communication systems, vector
high-order modulation is deployed. In Ref. [21], by using an on–
off-keying (OOK) baseband signal, the 4-ary quadrature ampli-
tude modulation (4-QAM) mm-wave signal is generated.
However, the method mentioned in Ref. [21] is complex and
costly. Instead, the external modulator is employed to realize
vector mm-wave signal generation with the aid of photonic fre-
quency multiplication and pre-coding techniques or without
precoding
[22–39]
, and the system is simple and cost effective. It
has the advantages of high stability, high purity, and significantly
less bandwidth requirement for transmitters. However, in
Refs. [22–39], it cannot generate high-speed vector mm-wave
signals due to the limitation of the digital-to-analog converter
(DAC) bandwidth. Moreover, the system cannot be integrated
by using photonic technology.
In this Letter, we proposed a novel and simple scheme of pho-
tonic aided vector mm-wave signal generation without a DAC.
In our scheme, two intensity modulators (IMs) are utilized, one
of which is driven by the baseband signal to generate an optical
signal carrying data, and the other operates at its maximum
transmission point (MATP) and is driven by a clock signal to
generate two second-order optical subcarriers. The experiment
results demonstrate that the bit error rate (BER) of the 20 Gb/s
4-QAM mm-wave signal can reach below the hard-decision
forward-error-correction (HD-FEC) threshold of 3.8 × 10
−3
after a delivery over 1 m wireless distance. Based on our pro-
posed scheme, we can generate high-speed vector mm-wave sig-
nals without a DAC, and it can reduce the system cost. Besides,
the system based on our scheme can be integrated by using pho-
tonic technology to simplify the system structure effectively.
We believe that our proposed scheme has potential applications
in future high-speed optical communication.
2. Principle
The schematic diagram of our proposed scheme is shown in
Fig. 1. As shown in Fig. 1, the system is composed of a laser diode
(LD), two Mach–Zehnder modulators (MZMs), a polarization
maintaining optical coupler (PM-OC), a polarization beam
combiner (PBC), an attenuator (ATT), a phase shifter (PS), a
polarization rotator (PR), and a photodiode (PD). The optical
signal from the LD is split into two paths by a PM-OC, and
the two paths are modulated by two MZMs, respectively. The
baseband data-1 mixed clock signal is used to drive MZM1,
and the baseband data-2 mixed clock signal is used to drive
MZM2, respectively. The PS is used to generate phase shifting
Vol. 19, No. 1 | January 2021
© 2021 Chinese Optics Letters 011101-1 Chinese Optics Letters 19(1), 011101 (2021)