  Lenses, optics and dependent lenses (or equivalently morphisms of containers,
or equivalently natural transformations of polynomial functors) are all widely
used in applied category theory as models of bidirectional processes. From the
definition of lenses over a finite product category, optics weaken the required
structure to actions of monoidal categories, and dependent lenses make use of
the additional property of finite completeness (or, in case of polynomials,
even local cartesian closure). This has caused a split in the applied category
theory literature between those using optics and those using dependent lenses.
The goal of this paper is to unify optics with dependent lenses, by finding a
definition of fibre optics admitting both as special cases.
