  Quantum Key Distribution (QKD) is a technology that allows secure key
exchange between two distant users. A widespread adoption of QKD requires the
development of simple, low-cost, and stable systems. However, implementation of
the current QKD requires a complex self-alignment process during the initial
stage and an additional hardware to compensate the environmental disturbances.
In this study, we have presented the implementation of a simple QKD with the
help of a stable transmitter-receiver scheme, which simplifies the
self-alignment and is robust enough to withstand environmental disturbances. In
case of the stability test, the implementation system is able to remain stable
for 48 hours and exhibits an average quantum bit error rate of less than 1\%
without any feedback control. The scheme is also tested over a fiber spool,
obtaining a stable and secure finite key rate of 7.32k bits per second over a
fiber spool extending up to 75 km. The demonstrated long-term stability and
obtained secure key rate prove that our method of implementation is a promising
alternative for practical QKD systems, in particular, for Cubesat platform and
satellite applications.
