  We introduce an electro-optical arrangement that is able to produce time-bin
encoded symbols with the decoy state method over a standard optical fiber in
the C-band telecom window. The device consists of a specifically designed pulse
pattern generator for pulse production, a field-programmable gate array that
controls timing and synchronization. The electrical pulse output drive a
sequence of intensity modulators acting on a continuous laser that deliver
bursts of weak optical pulse pairs of discrete intensity values. Such
transmitter allows for the generation of all the quantum states needed to
implement a discrete variable Quantum Key Distribution protocol over a
single-mode fiber channel. Symbols are structured in bursts; the minimum
relative delay between pulses is 1.25 ns, and the maximum symbol rate within a
burst is 200 MHz. We test the transmitter on simulated optical channels of 7dB
and 14dB loss, obtaining maximum extractable secure key rates of 3.0 kb/s and
0.57 kb/s respectively. Time bin state parameters such as symbol rate, pulse
separation and intensity ratio between signal and decoy states can be easily
accessed and changed, allowing the transmitter to adapt to different
experimental conditions and contributing to standardization of QKD
implementations.
