  We compare two possible ways of defining a category of 1-combs, the first
intensionally as coend optics and the second extensionally as a quotient by the
operational behaviour of 1-combs on lower-order maps. We show that there is a
full and bijective on objects functor quotienting the intensional definition to
the extensional one and give some sufficient conditions for this functor to be
an isomorphism of categories. We also show how the constructions for 1-combs
can be extended to produce polycategories of n-combs with similar results about
when these polycategories are equivalent. The extensional definition is of
particular interest in the study of quantum combs and we hope this work might
produce further interest in the usage of optics for modelling these structures
in quantum theory.
