Normal subgroups of braid groups

There is a lot of normal subgroups in braid groups (for example there is an action of $B_n$ on unitriangular bilinear forms on $R^n$ over arbitrary commutative ring $R$: $b_i\colon e_j\mapsto e_j$, $j\ne i, i+1$, $b_i\colon e_{i+1}\mapsto e_i$, $b_i\colon e_i\mapsto e_{i+1}-(e_i, e_{i+1})e_i$ and set $R=\mathbb Z_m$).

Is there any classification (with no conditions on terms of classification) of normal subgroups of $B_n$?

update: the interesting case of this classification for me is the case of finite index normal subgroups. For example I don't even know what is the kernel of the action described above. The answer may be useful in algebraic geometry (see A.L. Gorodentsev, TRANSFORMATIONS OF EXCEPTIONAL BUNDLES ON $\mathbb P^n$)